Meta Platforms, Inc. (META.US) shares fell sharply on Thursday, declining more than 3.4% to $574.3 at the time of writing. Alphabet (GOOG.US, GOOGL.US) also dropped over 1.3%. The decline follows a landmark ruling by a U.S. jury that Meta and Alphabet's Google must pay damages to a 20-year-old woman who claimed her addiction to social media triggered a mental health crisis. The outcome suggests significant legal risks for both companies as they face thousands of similar lawsuits. This marks the second legal defeat for Meta this week. On Tuesday, a jury in New Mexico found the company liable for misleading local teenagers about safety despite knowing that Facebook and Instagram had become breeding grounds for sexual predators, resulting in a $375 million civil penalty.