A case brought against Google in 2013 claims it violates a federal wiretap law, as well as several state privacy laws, by intercepting, reading, and mining the content of messages sent through its Gmail service, which has 104 million users in the U.S. The information, the suit claims, is used to target ads and build user profiles.

Privacy experts say the case raises important questions about how companies such as Google and other Internet companies make money from user data for a digital ad market that generated $42 billion in the U.S. last year. (Yahoo!, Facebook, and LinkedIn (LNKD) are facing similar actions.)