I don't think the "threat" is the obvious one... Nobody trusts Facebook -- many, if not most, people honestly believe they listen to their conversations already. The real message is how emotional and immature the leadership is to a perceived slight.
A message that said "Cigarettes will kill you" didn't stop smokers, and some label won't stop Facebook users or meaningfully impact Facebook. Hell, when Microsoft faced anti-trust breakup, the company didn't sit and whine. They fought the threat and sold billions of dollars of software and solutions to their antagonist.