John Timmer reports at Ars Technica:

The court responded to this request by pursuing an extraordinarily rare course of action: it read Facebook’s entire terms of service. And, in this case, their vague language—typically used to provide broad immunity—became a liability: “[the document] does not establish that users consented to the scanning of their messages for advertising purposes, and in fact, makes no mention of ‘messages’ whatsoever.”

Be specific with those Terms of Service. Really specific.