The ease and frugality of investing in the stock market through index funds has made indexing so popular that no less an authority than John Bogle, the chairman of Vanguard and the instigator of the trend more than 40 years ago, felt compelled to issue a warning: Indexing conceivably could become so ubiquitous, albeit well into the future, that the stock market essentially ceases to function, MarketWatch reports.

Because no good deed goes unpunished and the law of unintended consequences tends to be strictly enforced, Bogle and Vanguard likely would receive much of the blame if that ever happened. They would be convenient scapegoats, even if some scorn might be owed to all those high-priced professionals who run actively managed portfolios and can’t squeeze out a percentage point of extra returns every year to compensate for the difference in expenses.