Here's what 6 of the most powerful Wall Streeters have to say about bitcoin

By many measures, 2017 appears to be the year of cryptocurrency, but Wall Street's most powerful players are not on board with the craze.

The market for cryptocurrencies, digital coins powered by so-called blockchain technology, is up by more than 720% since the beginning of this year, at $145 billion.

Bitcoin, the first and largest cryptocurrency, is up more than 350% since the beginning of the year. It is seen as the most crowded trade to a pool of 214 fund managers overseeing $629 billion, according to a survey conducted by Bank of America Merrill Lynch.

At the same time, initial coin offerings, a cryptocurrency-based fundraising method, have taken off with hundreds of startups using the method to raise, in some instances, millions of dollars in a matter of seconds.

On top of that, over 75 crypto "hedge funds" have popped up to invest in the more than 1,000 cryptocurrencies on the market and initial coin offerings.

The massive growth of the market has piqued the interest of folks from Main Street to Wall Street, but Wall Street's top execs — who have seen their fair share of bubbles — are concerned.

Since the beginning of the month, a number of top Wall Streeters have weighed in on the bitcoin debate. Here's what six of them have had to say:

Jamie Dimon, CEO of JPMorgan

Jamie Dimon, CEO of JPMorgan, got the bitcoin conversation among top Wall Streeters this year going when he bashed it at the Barclays Financial Services Conference on September 12.

Dimon called it "a fraud" and said it was "worse than the tulip bulbs."

He added that he would fire any banker at the firm who traded the red-hot digital currency.

The morning after Dimon's remarks, the price of bitcoin tanked 11%.

Ray Dalio, co-CIO of Bridgewater Associates

Ray Dalio, the founder of the world's largest hedge fund, echoed Dimon's criticisms of bitcoin on September 19.

The billionaire founder of Bridgewater Associates said bitcoin "is a bubble" during an appearance on CNBC's Squawk Box.

Dalio's beef with bitcoin, specifically, is that it isn't a good store of value and it's hard to make transactions with, the two criteria Dalio sees as essential for a currency.

"Bitcoin, today, you can't make much transactions in it," Dalio said."You can't spend it very easily."

Dimon (Part II)

Dimon doubled down on his anti-bitcoin position on September 22, saying cryptocurrencies like bitcoin and ether "are a kind of novelty."

While talking to CNBC India, the banker went after cryptocurrencies and initial coin offerings, a red-hot cryptocurrency-based fundraising method.

"It's creating something out of nothing. That to me is worth nothing," Dimon said of ICOs. "It'll end when people lose a lot of money."

To raise money through an ICO, companies create their own digital coin or token. Investors have poured into ICOs this year, with some companies raising millions of dollars in a matter of seconds from a token sale.

In total, more than $2 billion has been raised via ICOs, according to Autonomous NEXT, a financial technology analytics firm.

James Gorman, CEO of Morgan Stanley

James Gorman took a more moderate stance on the cryptocurrency than Dimon or Dalio at a conference hosted by The Wall Street Journal on September 27.

Gorman said he thought bitcoin was "certainly more than just a fad."

Still, though Gorman sees some potential in the digital coin, he has not invested in it.

"I've talked to a lot of people who have," Gorman said. "It's obviously highly speculative, but it's not something that's inherently bad. It's a natural consequence of the whole blockchain technology."

Larry Fink, CEO of BlackRock

Larry Fink, the head of the largest investor in the world, BlackRock, sees huge potential in blockchain, the underpinning technology of digital currencies like bitcoin, but he's not on board with the cryptocurrency craze.

In a recent interview with Bloomberg News last week, Fink said he thinks the explosive growth of bitcoin points to nefarious behavior.

"It just identifies how much money laundering there is being done in the world," Fink said. "How much people are trying to move currencies from one place to another."

That said, Fink is on board with a "true global digital currency."

"But let's be clear if we created a true global digital currency - I hate the word crypto - then you would not have money laundering anymore you would have everything understood, everything would be flowing through," he said.

Lloyd Blankfein, CEO of Goldman Sachs

The same day Fink came out against bitcoin, Lloyd Blankfein, the CEO of Goldman Sachs, tweeted about the cryptocurrency.

Blankfein said he's "still thinking about bitcoin" and that he was not flat out endorsing or denouncing the digital currency.

The day before Blankfein's tweet, The Wall Street Journal reported that Goldman Sachs is in the very early stages of potentially setting up a bitcoin trading operation.

"In response to client interest in digital currencies we are exploring how best to serve them in this space," a Goldman spokesperson told The Journal.

If Goldman follows through, it would be the first blue-chip financial services firm to break into the cryptocurrency market, which this year has exploded in value by more than 720% to $145 billion.

Axel Weber, UBS Chairman.

On Wednesday Alex Weber, chairman of UBS, the $3 trillion financial services firm, said bitcoin doesn't fit the bill to be considered a currency, according to a report by Reuters.

“I get often asked why I‘m so skeptical about bitcoin, it probably comes from my background as a central banker,” Weber said at a conference, according to Reuters' Joshua Franklin.

“The important function of a currency is, it’s a means of payment, it has to be generally accepted, it has to be a store of value and it’s a transaction currency," Weber added. "Bitcoin is only a transaction currency.”