In all likelihood if I had access to Google or FB data I could get reams of personal information on ex-s and make their life hell. I could find out secrets about local business owners. I could use the data to imply all kinds of untrue things about said person just for the sake of being a dick.

There's an interesting point Dan Geer made about identities for state-level spying activities. If he were to do something illegal (shall we say) in a place he shouldn't, with the level of information collected across the whole of the network, it would be far more feasible to borrow somebody else's identity for the work than it would be to create a plausible fake person from the ground up.

Our database identities are skins for spies now, you want to be caught in that game?