Bitcoin was one of the biggest topics of 2017. The cryptocurrency rose to meteoric heights towards the last few months of the year. Some vendors are accepting it as payment (Overstock and Expedia) and it is becoming a technology that major financial institutions use. However, given it’s rising popularity, the question remains: is Bitcoin just a new trend? A former Nobel-prize winner thinks so.

American economist Robert Shiller compared Bitcoin to the bimetallism fad in the late 1800s, which saw both gold and silver accepted as legal tenders. On the markets side of things, he discussed seeing some worrying signs in his data relating to the 1987 stock crash. On CNBC’s “Closing Bell” he said, “confidence in the valuation of the market is indeed the lowest it’s been since 2000. And when it got low in 2000, the market fell about 40%. So it was bad.”

Shiller is not the only person who has doubts about Bitcoin. In a critique of the cryptocurrency, JPMorgan Chase & Co. CEO Jamie Dimon said, “The currency isn’t going to work. You can’t have a business where people can invent a currency out of thin air.”

Recently, certain financial platforms have rejected firms trading the cryptocurrency as clients. Founder of the crypto-asset investment firm Zinica Group, Oz Eleonora claimed that there is a major obstacle for financial platforms due to reputational risk. He said, “If you introduce a bitcoin fund without addressing the compliance properly, you’ll anger both the regulator and your client base.”

With financial platforms casting doubt about using Bitcoin, people may begin to wonder if Bitcoin has longevity. Morgan Stanley CEO James Gorman said, “the concept of anonymous currency is a very interesting concept—interesting for the privacy protections it gives people, interesting because what it says to the central banking system about controlling that.”

It remains to be seen whether Bitcoin simply a fad that fades away. It will be intriguing to see how the market for Bitcoin develops in 2018.