The most common excuse to justify invading other people's privacy is for security purposes. To some extent, I agree, but this can be abused, and it does not mean that we need to be monitored for everything we do. That's the way I see our future headed though, no privacy at all and everything being monitored, maybe even when you go to the bathroom (in or out of your own home)? May sound funny, but I hope it doesn't get to that point.
Facebook is probably the worst for invading privacy though I would say.
