27 Jul 2018
Cambridge Analytica: Data influenced 2016 US election
Facebook's stock plunged twenty-percent overnight after the company said it expects revenue growth to slow as it "puts privacy first" and rethinks how users interact with the site. Wall Street's sharp reaction followed an earnings report that showed slower than expected growth in user numbers and ad revenue. The stock rebounded slightly as the evening wore on, but the news clearly spooked investors. Philippa Tolley speaks to the BBC's technology correspondent Rory Cellan-Jones, who explains how it happened.