"I know exactly what’s there, it’s a ‘Pyramid’ scheme. You only make money based on people who enter after you… It has no real utility in the world. They’ve been trying to create a utility for it for 10 years now, so it’s a solution in search of a problem and it still hasn’t found a problem to solve."

"Mark Dow, a former US Treasury and International Monetary Fund economist, says that there’s no recovery coming. “Bitcoin is dying,” he boasted on Twitter."

"All cryptos will disappear."

"#Bitcoin will be dead by 2030. Average currency life = 27 years."

"…we won’t be reading much about “decentralization” here anymore. That watchword for a generation of young men interested in building the future as developers, programmers and blockchain and crypto enthusiasts, is well, kind of dead."

"Not many are able to think long term and realize this, but the cryptocurrency markets have already topped. With summer ending soon, the next 50% price cut might be only a few weeks away. Good news! I was (finally) able to verify and unfreeze an account with a crypto exchange and cashed out most of my money out of this MLM scheme."

"Even the smartest dealmakers in the world have been fooled by hype, and overestimated an asset’s true value. Bitcoin will end up virtually worthless, just like Tumblr, because its true value is next to nothing."

"Bitcoin remains sparsely adopted even a decade after its birth. We demonstrate theoretically that this limited adoption arises as an inescapable equilibrium outcome rather than as a transient feature."

"I won't be talking about Bitcoin in 10 years, I can assure you that. […] I would bet in even 5 or 6 years I'm no longer talking about Bitcoin as Treasury Secretary. […] I can assure you I will personally not be loaded up on Bitcoin."

"Who let the fools out? The only plausible explanation was an article written as an April Fool’s joke reporting that the SEC had held an emergency meeting over the weekend and voted to approve two bitcoin-based exchange traded funds (ETFs). For true fools, it hardly mattered what sparked the rally. As long as prices are going up, fools will buy in hopes of selling to greater fools. At some point, the supply of greater fools will dry up and bitcoin’s second bubble will end just like the first."

"Cryptocurrencies are a pure gamble with no discernible fundamentals whatsoever. The cryptocurrency “markets” are rife with fraud, scams and manipulation. I’d love them if I were a con artist."

"I am not a fan of Bitcoin and other Cryptocurrencies, which are not money, and whose value is highly volatile and based on thin air."

"I hope I am wrong and there turns out to be a bright future for Bitcoin. The facts say otherwise."

"Indeed Bitcoin is now down below 10k. Has lost a third of its value in less than a week. Still a long way to less than zero as its true value is negative not zero given its toxic externalities! It will get to zero in due time."

"To me, it's fool’s gold. There are no financial statements, no balance sheets, no revenues or assets. There’s not even a physical product! This is unbridled lunacy in which some astute techies take advantage of what will ultimately be some very unfortunate people."

"Bitcoin has no intrinsic value as an asset. Never had. It yields no cash, generates no income and serves no useful legal purpose. It is most useful for money-laundering. If you need to get your money out of the country, fast, bitcoin is a pretty good way to do it."

"I’ve witnessed several asset bubbles over the years and those trapped inside also say foolish things to rationalize the price rise. But none more foolish than what’s being said to rationalize the Bitcoin bubble. The bigger the bubble, the more foolish one must be not to see it!"

"People are going to wake up one day and not find that the value of their BTC investment is diminishing, but that it is zero."

"Despite the utopian claims of its proponents, Bitcoin is a right-wing nightmare which facilitates tax evasion, money laundering and environmental degradation."

"My position remains the same. #Bitcoin will likely be replaced by a new technology and it’s manipulated. It’s possible it’s built to last, but not probable, so keep your position to an amount you’re willing to loose For most, that’s 1-5% of net worth It will likely go to 0-$500."

"As I’ve said before, bitcoin is nothing more than a confidence game. It’s worth nothing if people suddenly lose their confidence in this fake digital currency. It’s backed by nothing. It’s the definition of a con. I’ve said the same thing when a bitcoin was selling for $20,000. And still was saying it when it plunged to $4,000. Its real worth: $0."

"Bitcoin will soon be worth zero. But until then criminals will still be able to use it and other digital currency to move money around the world without being caught."

"Don’t be fooled by #bitcoin’s recent bump. Buying bitcoin is a fool’s game."

"Bitcoin is essentially a “digital game” and is “worthless,” “Shark Tank” investor Kevin O’Leary told CNBC on Tuesday. “It is a useless currency,” O’Leary, chairman of O’Shares ETFs, said on “Squawk Box. "To me, it’s garbage, because you can’t get in and out of it in large amounts.”"

"“It’s a gambling device… there’s been a lot of frauds connected with it. There’s been disappearances, so there’s a lot lost on it. Bitcoin hasn’t produced anything,” Buffett told a group of reporters ahead of Berkshire Hathaway’s annual meeting at the CHI Health Center in Omaha, Nebraska. “It doesn’t do anything. It just sits there. It’s like a seashell or something, and that is not an investment to me,” he added."

"Bitcoin is up 6% to its yearly high of around $6,000. Don’t be fooled, a 6% uptick is nothing after its huge plunge. Bitcoin is unreliable and susceptible to fraud, it is not a currency, but nothing more than a highly-speculative asset"

"First of all, the cryptocurrencies don’t actually work as currency. That’s the big deal. They’re hard to buy because they are deliberately incompatible with the rest of the financial system. They’re incredibly hard to hold on to because, well, something goes wrong it’s “Sorry for your loss.” That’s a function of the irreversible design. And finally, they’re actually really hard to spend. Most merchants who accept cryptocurrency aren’t actually accepting cryptocurrency, they’re using a service that turns it into dollars."

"To be clear, Bitcoin is absolutely worthless by any real measure. It’s fake money that’s about as practical to use in the real world as Monopoly bills. Bitcoin is backed by nothing and requires tremendous amounts of energy to mine using computers. As it becomes more difficult to mine, it saps more and more energy, causing millions of tons of carbon dioxide to be pumped into the atmosphere and accelerating climate change. Bitcoin is little more than a speculator’s death cult at this point."

"The big fatal flaw is that it doesn’t actually work as currency. If you can’t use it as a competitor to all the other actual digital currency systems we have, like, oh, PayPal…. All of these payment systems are vastly more efficient than the cryptocurrencies, unless you’re interested in criminal activity."

"I know who's the guy behind Bitcoin and when that comes out Bitcoin is going to Zero."

"Cryptocurrencies are scams and anybody who puts any money into them and loses the lot only has themselves to blame."

"“Bitcoin has no unique value at all,” Buffett told CNBC’s Becky Quick in a “Squawk Box” interview Monday. “It is a delusion, basically.”"

"But that dream is now effectively dead, and blockchain is now fully into its boring phase. The latest and most telling evidence of this arrived this morning, when JPMorgan (JPM) said it had developed and tested a prototype of a digital coin."

"Decentralization requires a process of intensive validation in the consumption of resources, which reduces system efficiency. In contrast, centralized systems with an intermediary trusted by the parties allow the design of much simpler and cheaper systems."

"Honestly, cryptocurrencies are useless. They’re only used by speculators looking for quick riches, people who don’t like government-backed currencies, and criminals who want a black-market way to exchange money."

"Primarily all we do with bitcoin is that we trade it. That is awfully similar to tulips and Beanie Babies in their heydays ― and we all know what happened to them. So it is a not a question of if, but more a question of when bitcoin will go to zero."

"In conclusion, it is a dismal space. Private and permissioned blockchains are an old idea—a good idea—just with a new buzzword on it. The public blockchains are grossly inefficient. The cryptocurrencies don’t work to provide anything against drugs and ransoms and stuff like that. Smart contracts are an unmitigated disaster unless you like comedy gold. And the field is just recapitulating 500 years of failures. So in the end, the only winning move is not to play—unless you like playing with flamethrowers."

"“I do believe it will go to zero. I think it’s a great technology but I don’t believe it’s a currency. It’s not based on anything,” Jeff Schumacher, founder of BCG Digital Ventures, said during a CNBC-hosted panel in Davos, Switzerland."

"Does the subsequent price behavior of bitcoin mean my prediction was wrong? No. I still think that the long-run equilibrium price of bitcoin is zero. It just hasn’t bitten the dust yet."

"Ardo Hansson, the governor of Bank of Estonia, has claimed that cryptocurrencies would die as a complete load of nonsense while speaking at “5 Years with the Euro” conference in Latvia. The policymaker assured that the bubble has already started to collapse and it should continue to do unless the market reaches “a new kind of equilibrium.” “I think we will come back a few years from now and say how could we ever have gotten into this situation where we believed this kind of a fairy-tale story,” said Hansson."