Thanks to the Like buttons scattered all over the web Facebook probably knows a lot about you before you even sign up, they can simply keep a record of your IP

Thanks to the Like buttons scattered all over the web Facebook probably knows a lot about you before you even sign up, they can simply keep a record of your IP address/browser signature and the sites you visit. I wonder if they'll use this data to recommend interests when you sign up. I've blocked all Facebook domains in my hosts file for this reason. Yes, I'm a bit paranoid.