SHARES IN GAMESTOP, an American video-game retailer, resumed their wild ride on January 29th, after some brokers eased restrictions on trading in the stock. When the market closed, the shares were priced at $325-up by 68% on the day and a long way from the $20 they were fetching back on January 12th.

The saga, which has appeared to pit retail investors against the titans of Wall Street, has drawn regulators' attention. The Securities and Exchange Commission (SEC) warned that “extreme stock price volatility has the potential to expose investors to rapid and severe losses and undermine market confidence”, and said that “we will act to protect retail investors when the facts demonstrate abusive or manipulative trading activity that is prohibited by the federal securities laws.”