Elon Musk, Bill Gates and Janet Yellen are sending bitcoin tumbling - CNN

In an interview with Bloomberg, Gates said that it was one thing for Musk and Tesla to invest in bitcoin, but that doesn't mean average investors should follow that lead.

"I do think people get bought into these manias, who may not have as much money to spare, so I'm not bullish on bitcoin," Gates said.

"My general thought would be that, if you have less money than Elon, you should probably watch out."

And in case you're keeping score at home, everybody except Amazon (AMZN) CEO Jeff Bezos has less money than Elon — including Bill Gates.

It's also worth noting that Gates, like his good friend Warren Buffett, has been bearish on bitcoin for some time — a position that could have lost average bitcoin investors a lot money if they had listened to him.

In fact, Gates said in 2018 that he would short bitcoin if there were an easy way to do it.

The cryptocurrency was trading for less than $10,000 at the time.

Despite the recent pullback, bitcoin prices are still up more than 65% so far in 2021.