Cops are everywhere That's their Job.
You Don't visit webpages with You passport or your face showing it lol

You visiting some website You dont leave there You full name lol : D
just to Proof Something for cops over the internet its not easy.
its internet anyone can even Hack in your PC and use it.
nowdays you can be as much as victim as criminal.
Only way they can have something on you if they can see the dirty money come to you some ways.
but That's Why we have bitcoins.
and what is this panic about Facebook not safe???
Facebook is not FBI CIA Facebook is Business all they Care about is the money!
Facebook care about only if some user might harm their reputation or doing something Bad in facebook (not Bad Morally , but Bad for their business)