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Photo illustration by Money; AP (4)

It's no secret that the digital currency Bitcoin has been on a tear. With prices rising five-fold this year, investors have been throwing around the "b" word: Bubble.

Now that Bitcoin may have peaked — its price briefly hit $5,000 on Sept. 1 before tumbling 21% over the past two weeks to $3,975 on Tuesday — you're likely to be hearing even more about that.

Here are 10 investing experts who told you it was going to happen:

Jamie Dimon

Bio: Chief executive of JPMorgan Chase

Take on Bitcoin: Speaking at a financial conference last week, Dimon didn't mince words, calling Bitcoin a "fraud" and comparing investors' interest in it to the bizarre tulip craze that swept the Netherlands in the 1600s.

"The currency isn’t going to work," he said, according to Reuters. "You can’t have a business where people can invent a currency out of thin air and think that people who are buying it are really smart.”

Dimon didn't say when the Bitcoin bubble would burst, only that it would end badly. “Don’t ask me to short it. It could be at $20,000 before this happens, but it will eventually blow up.” he said. “Honestly, I am just shocked that anyone can’t see it for what it is.”

Mohamed El-Erian

Bio: Chief economic adviser of Allianz SE; former chief executive Pimco; former head of the Harvard University endowment.

Take on Bitcoin: El-Erian, appearing on CNBC's Squak Box last week, doled out praise for Bitcoin's so-called "blockchain" technology. But, at the same time, he warned: "I think the price is gonna blow up."

"It is a disruptive technology, but the current pricing assumes massive adoption, and I don't think that governments will allow the amount of adoption that is currently priced in," El-Erian said. Pressed on what price might be justified — Bitcoin was then trading at around $4,000 — he speculated: "I would say at least half of what it is, a third of what it is."

Warren Buffett

Bio: Chief executive of Berkshire Hathaway and the world's second-richest person.

Take on Bitcoin: Buffett doesn't speak out on Bitcoin very often. But he did reveal his views in a CNBC interview in 2014. Like El-Erian, Buffett acknowledged Bitcoin's technology was intriguing. "It's a method of transmitting money," he said. "It's a very effective way of transmitting money and you can do it anonymously and all that. A check is a way of transmitting money, too...I hope Bitcoin becomes a better way of doing it."

But, but he went on to add that Bitcoin had no intrinsic value, undercutting its prospects as an investment. "Stay away from it. It's a mirage, basically," he said.

Mark Cuban

Bio: Billionaire co-founder of Broadcast.com and Shark Tank star

Take on Bitcoin: As early as June, Cuban tweeted that Bitcoin was in a speculative bubble. Cuban may be of two minds, however. In August, news reports suggested he had backed a venture capital firm with plans to invest in Bitcoin-like technology and start-ups looking to launch Bitcoin rivals.

Robert Shiller

Bio: Nobel-prize winning Yale University economist; widely regarded as an expert of financial bubbles after predicting the 1999 dotcom and 2006 housing crashes.

Take on Bitcoin: When online news site Quartz asked Shiller earlier this month for the best example of a speculative bubble right now, he didn't hesitate: "The best example right now is Bitcoin. And I think that has to do with the motivating quality of the Bitcoin story. And I’ve seen it in my students at Yale. You start talking about bitcoin and they’re excited!"

He went on: "Somehow Bitcoin [gives you] a sense of empowerment: I understand what’s happening! I can speculate and I can be rich from understanding this! That kind of is a solution to the fundamental angst."

Ray Dalio

Bio: Founder of Bridgewater Associates, the world's largest hedge fund

Take on Bitcoin: In theory, bitcoin could be a functional currency, Dalio told CNBC this week. But in reality, all the speculation surrounding Bitcoin, coupled with the inability to use it as cash in much of the commercial world, makes that difficult, he said.

"You can't make much transactions in it. You can't spend it very easily," he said on CNBC, adding: "It's not an effective (store) of wealth because it has volatility to it, unlike gold. Bitcoin is a highly speculative market. Bitcoin is a bubble."

Seth Klarman

Bio: Billionaire hedge-fund manager

Klarman is known for keeping a low-profile. Earlier this year, The New York Times dubbed him, "the most successful and influential investor you have probably never heard of." But in a 2014 letter to investors, Klarman warned them against getting swept up in Bitcoin mania.

“Only in a bull market could an online ‘currency’ dubbed bitcoin surge 100-fold in one year, as it did in 2013," he wrote, referring to an earlier run-up.

While conceding the cryptocurrency "may contain a kernel of rationality," he concluded: "Bitcoin is yet another bandwagon we are happy to let pass us by."

Jim Rogers

Bio: Famed hedge fund manager

Take on Bitcoin: The commodity investor admitted to having "completely missed it" on Bitcoin in a Youtube interview posted earlier this month. While speculating that the technology underneath Bitcoin may someday lead to riches, he insisted Bitcoin's recent trajectory had all the hallmarks of a speculative bubble:

Jeffrey Gundlach

Bio: Founder of DoubleLine Capital

On a webcast with investors last week bond fund manager Jeffrey Gundlach related how his 86-year-old mother texted him a link to a story about Bitcoin and wondered whether she too should jump in, according to a Business Insider report.

Gundlach, who noted he had a hard time believing the currency truly could not be hacked, told investors, "I’m going to let this mania go on without me." He suspects his mom has changed her tune too. "I'm sure she's not interested in buying it now that it's falling," he says.

Ben Bernanke

Bio: Former Federal Reserve chairman

In a 2013 letter to Congress Bernanke said digital currencies "may hold long-term promise, particularly if the innovations promote a faster, more secure, and more efficient payment system." Later, however, in a 2015 interview with Quartz, he outlined serious reservations.