Tech Shares Tumble Again as Regulatory Risks Rattle Investors

But tech shares were hit the hardest, dragging down the broader market in the final hour of trading. A series of recent developments pointed to more government oversight of the industry. Facebook Chief Executive Mark Zuckerberg is planning to testify before Congress about the social-media company's privacy and data-use standards, according to people familiar with the matter. The company's shares fell 4.9% on Tuesday and are down 15% this month over concerns about its handling of user data, on track for its worst monthly decline since 2012. The Federal Trade Commission, in a statement Monday, signaled that it is conducting a broad probe of Facebook, while 37 state attorneys general are also demanding explanations for its practices.