Facebook has hired one of the top antitrust lawyers in Silicon Valley in a sign that the company could be preparing for war with Donald Trump's administration. Kate Patchen, the chief of the Department of Justice's antitrust division in San Francisco, has joined Facebook as director and associate general counsel of litigation. Patchen's hire comes during the same month that US President Donald Trump said his administration was "looking at" antitrust proceedings against tech giants Google, Amazon, and Facebook.