In a year that has seen digital currency prices go higher not by percentages but multiples, investors are starting to worry that things have gone a bit too far.
is now considered the "most crowded trade," as measured by sentiment in the monthly global Bank of America Merrill Lynch Fund Managers survey. That means investors believe there are too many people on one side of the trade and it could be due for a reversal.
Bitcoin's price has surged about 330 percent this year, the beneficiary of a jump in interest for the cryptocurrency and a growing field of competitors, as well as a flight to alternative assets and, some fear, a speculative bubble.
The Merrill survey is one of the most followed and respected on Wall Street. Conducted during the week that ended Thursday, more than 200 global fund managers with at least $600 billion under management were surveyed.
Of course, a crowded trade doesn't have to mean it's nearing an end.
In the BofA survey, bitcoin supplanted the Nasdaq and the short dollar trade as the most crowded. Bitcoin got 26 percent of the vote, edging out the Nasdaq, with 22 percent and the bet against the greenback, which took 21 percent of the vote.
The two other "crowded trades" have done very well this year, with the Nasdaq surging just shy of 20 percent and the dollar tumbling nearly 10 percent against a basket of its global competitors.
In addition to worries over the bitcoin trade, fund managers are backing away from U.S. stocks. The collective allocation to domestic equities fell to a net 28 percent underweight, which is the highest level since November 2007, shortly after the market hit its precrisis highs.
Investors also are beginning to fret about global growth, even as economists are upgrading their expectations. Just 25 percent expect a stronger global picture over the next 12 months, down from 62 percent at the beginning of 2017.