In defense of the Facebook sign up, how about issues of safety? Meeting a stranger online can be risky. Forcing signup via Facebook helps provide data that user

In defense of the Facebook sign up, how about issues of safety? Meeting a stranger online can be risky. Forcing signup via Facebook helps provide data that users can use to perform a due diligence on the strangers they might be meeting. It helps hold people accountable if they do decide to do something malicious offline. Perhaps LinkedIn might be better, but I don't see a problem with utilizing some sort of identity related social sign up for this idea.