Image via Wikipedia
According to Zuckerberg, privacy is a thing of the past. Well kiss my ass ;-)
My suggestion has always been to be mindful of what you share and be very clear about who really owns the data. Even if you've unknowingly hired an ad broker (aka GOOG), or photo curator (aka flickr) or you've decided against learning basic HTML so that you could quickly host a webpage and share pictures with friends (aka myspace and facebook)... You give up your rights almost immediately.