Robinhood, Citadel Threatened by SEC Chief’s Push for New Rules

Robinhood Markets and Citadel Securities had starring roles in the GameStop Corp. trading frenzy that rocked financial markets this year. Now, they have among the most to lose as U.S. regulators’ threaten a clean up.

In his most revealing comments so far about how Washington might respond to the meme-stock mania, Securities and Exchange Commission Chairman Gary Gensler shined a spotlight on online brokerages and market makers that dominate the business of executing retail investors’ equity orders.

He said popular apps like Robinhood’s exploit game-like features to keep customers trading -- an investing strategy that over time can eat into ...