Facebook is a privacy disaster. Nobody with an iota of sense really trusts it to respect their privacy. Which is precisely one of Path's big selling points: It's got better privacy. Or so it seemed. But then it surprised everyone. (Updated)
Path got caught uploading users' entire address books to its servers. It wouldn't have been a big deal if this was an opt-in action. But it wasn't. It happened in the background without most users' permission or even knowledge. This was a big surprise to a lot of people (even if Dave Winer did warn about it peeking at our address books in November of 2010.) It illustrates a huge point about privacy: Don't surprise people.