Ilon Musk and Katie Wood criticized passive investing on Twitter, taking part in a long-running Wall Street discussion about the growing power of index funds, Bloomberg writes.

The discussion was spearheaded by venture capitalist Marc Andreessen, who argued that companies like BlackRock have too much weight in many corporations because of their voting power, anchored by their huge passive funds under management.

Musk, who is the CEO of Tesla, responded that passive investing has “gone too far.” And Kathy Wood, who founded Ark Investment Management LLC, supported the discussion by noting that investors in the S&P 500 index missed out on the big gains in Tesla stock before the company was included in the index.

She said, “History will judge the accelerated shift to passive funds over the past 20 years as a massive misallocation of capital.”

And while Wood is one of the best-known money managers, it’s been a bad year for her, with shares of her flagship ARK Innovation ETF falling nearly 45%. Meanwhile, Tesla’s weighting in many major benchmarks means that companies such as Vanguard Group and BlackRock are the second and third largest shareholders of the electric car firm after Musk himself.

It’s worth noting that the debate over the risks of indexing, which directs cash flows into stocks virtually “on autopilot,” often regardless of a company’s fundamentals, has been ongoing for several years as passive funds have relentlessly wrested market share from active competitors. Their lower costs, combined with doubts about the ability of most managers to outperform the market, have fueled this shift.

But the reasoning on the other side is also becoming more sophisticated: active money managers are using liquid, easy-to-manage passive funds in their strategies and issuing their own exchange-traded funds to reduce costs and expand access, and creating strategies that blur the line between indexing and stock-picking.

Meanwhile, most passive strategies have long had a lot behind them, from writing the rules of each index to deciding how each fund will perform.

The conclusion, however, is that overall investment activity in the U.S. equity market has changed little over the past two decades.