The major news is stalking love interests,Remember in MiB when J uses surveillance satellites to check up on his love interest?
I don't know the granularity of FB access logging, but I imagine employees aren't verboten from looking up anything about anyone. At one time, it was a perk ("Join us and SPY ON ALL YOUR FRIENDS! LOL!").
There have been reports of google sysadmins stalking people (ex-lovers) by using their root-level gmail/account access. Supposedly google has since instituted finer grained access logging that will alert if someone is working outside of their authority (but, who locks down executive/CEO authority?).
I'm paranoid. I think, in Sergey's office, there's page that looks like google.com, but it flatly searches every gmail/gtalk/gvoice message ever sent or received. Their speciality is search and you give them all your private communications? Yeah, that'll end well.