Welcome to Law.com Class Actions: Critical Mass, a weekly briefing for class action and mass tort attorneys.

This week: The first trial against Johnson & Johnson since the dismissal of its two talc bankruptcies began in California. A federal judge in California refused to dismiss lawsuits alleging social media sites like Facebook and YouTube cause mental health problems in young users. Find out who is representing passengers of a Horizon Air flight that almost crashed when an off-duty pilot shut down the engines.