Bubble, Ponzi, tulip and trouble have been among the words used by crypto-critics over the past year as bitcoin powered from under $1,000 and passed the much talked about $10,000 marker.
Despite being talked down by some major financial names, not least JPMorgan CEO Jamie Dimon, it looks like cryptocurrencies could be here to stay.
Bitcoin has posted a return of over 900 percent since the start of the year with one technical trader saying the rise of bitcoin in 2017 is the biggest bull market he has seen in over 40 years of working in finance.
David Shrier, academic and CEO of Distilled Analytics, told CNBC that he has absolutely no doubt that there is feverish speculation going on with cryptocurrencies but that in itself is not a bad thing.
"There is enough utility and utilization of bitcoin that it will retain some kind of value, even if the price settles down a bit. Amazon didn't go to $0 when the dotcom bubble burst, but other frothy stocks with no reality behind them did. Similarly, bitcoin won't go to zero, but I do believe a number of these other cryptocurrencies will fail," Shrier said.
Dominic Williams, chief scientist at research group the DFINITY Project, is also skeptical about the viability of initial coin offerings (ICOs) in particular, saying "only a fraction of the projects holding ICOs have any chance of success." ICOs are a way for companies to raise money — people pay money in exchange for a token or digital currency. The token doesn't usually give the investor equity in the company. Instead, it can be traded or used to do something with the firm.
"The vast majority have been created specifically with the ambition of collecting money from enthusiastic investors rather than delivering utility in the real world," he said.
Meanwhile, Ken Griffin, the founder and CEO of hedge fund Citadel, is concerned that some investors are mixing up blockchain and bitcoin. Blockchain is a general term for a distributed digital ledger that can record transactions and is tamper-proof. It's the underlying technology that makes cryptocurrencies such as bitcoin and Ethereum possible. He told CNBC that many people buying it, do not understand the underlying technology.
A ramp up in retail accounts over the Thanksgiving holiday helped bitcoin over $10,000 and some in the financial industry are worried about the fallout of a possible price crash.
Shrier said he is not overly worried that a crypto-bubble "crash" will hinder bank acceptance of so-called distributed ledgers and added that "speculation helps attract new sources of risk capital and new entrepreneurs to the space."
"Other market forces will assert themselves eventually, and what will emerge out of that is a new way of operating," he told CNBC.
On bitcoin's price volatility, Williams explains that for a cryptocurrency to be used day-to-day, its value has to be stable otherwise it cannot be effective as a medium of exchange.
"The value of bitcoin is notoriously volatile because it is created mainly by the interaction of speculative demand, which makes application as a normal currency impossible for now," he said.
He is concerned though about the possibility that some people getting in on the action may get burned and bitcoin ends up being a kind of pyramid marketing scheme that leaves only the early buyers rich, with everyone else losing plenty of money.
"Only time will tell," he added.
The rally may not even be over yet, according to some commentators. The man who called bitcoin's rise to $10,000, fund manager Michael Novogratz, has over 20 percent of his net worth in cryptocurrencies and told CNBC that he sees the possibility of it reaching $40,000 by the end of next year.