Are Google, Facebook, Twitter users really concerned about this? I know people make a noise about privacy and data protection - but would this make you change platform?
Frankly, when you 'fix' Facebook's privacy issues, much of what people like about it doesn't work anymore.
e.g. People love to look up and keep tabs on old friends and flames on facebook. But you can't really do that with privacy settings that hide location, history and profile pictures by default, nor with 'groups' that allow those old friends/flames to share their updates/pictures only with their current friends/flames.
Higher-privacy is almost self-defeating for a social network with Facebook-style use.
Though it can be pretty key for things like Linked-In, where updates are less frequent, you don't have overlapping levels of formality between 'contacts', privacy is more-valued in that context, etc.