Social media services including Facebook Inc. and Reddit restrict discussions about weapons, drugs and other illegal activity, but their rules do not specifically mention another lucrative regulated good: stocks.

Some people think they should. Users of a Reddit group, in which 5 million members exchange investment ideas, generated significant profits by gorging on shares of GameStop Corp. and other out-of-favor companies that had been shorted by big hedge funds.

Investors have used social media for years. Anonymous posts have fueled cryptocurrency pump and dump schemes, according to studies, but that obscure market generated less scrutiny. The "Reddit rally" however, has roiled global stock markets and drawn scrutiny of posts in which thousands of smaller investors trade tips on platforms from Facebook to Instagram to Telegram and Clubhouse.