'Big Short' investor Michael Burry is calling passive investment a 'bubble.' He's not the only finance luminary sounding the alarm.

Jeffrey Gundlach, often called the king of bonds, also sounded the alarm on passive investing amidst a stock selloff in December 2018.

"I wouldn't advise anyone to be a passive investor," Gundlach told CNBC in an interview. "My strongest advice is to not invest in passive US equity funds."

"I think in fact that passive investing and robo-advisors ... are going to exacerbate problems in the market because it's herding behavior," Gundlach said.

Howard Marks, the cochairman of Oaktree Capital, dedicated an 18-page memo to the topic of index investing, saying that the vast growth of ETFs has coincided with the market rally that began 10 years ago, and that we haven't yet seen how they perform in a downturn.

"Might the inclusion and overweighting in ETFs of market darlings - a source of demand that may have driven up their prices - be a source of stronger-than-average selling pressure on the darlings during a retreat?" he asked.

He added: "We wont know until it happens, but it's not hard to imagine the popularity that fueled the growth of ETFs in good times working to their disadvantage in bad times."

Robert Shiller, the Nobel prize-winning economist, told CNBC's trading nation that "all this talk of indexes, it's a little bit diluting of our intellect. It becomes more of a game. It's a chaotic system," in an interview in 2017.

"The problem is that if you are talking about passive indexing, that is something that is really free-riding on other people's work, " Shiller said.

Jack Bogle, the late founder and chief executive of The Vanguard Group, was also the father of the index fund - he created the first one to track the returns of the S&P 500 in 1975.

In 2018, he too spoke out about the issues associated with his own invention. In an article in the Wall Street Journal, Bogle said that it's only a matter of time before index funds own half of all US stocks.

"I do not believe such a concentration would serve the national interest," he wrote.