1. Has it ever happened that you get a mail in one your various Email IDs from Facebook or some other site that you never linked up with....?I am sure if you are a regular browser on social networking sites,this must have happened once...and it must have kept you thinking...HOW ??
2. This happens when you have that email id open in some other tab and your Facebook account open in other...typically in a multitab session wherein you have opened many sites under one browser in various tabs..... that's when info gathering sites get your email id and things related to their interest.....TAKE CARE