It is certainly possible that FB has my personal email for the reason you suggest although I wonder why the message is always about 3 notifications and 7 friends. I'm a little alarmed that I have 7 friends I knew nothing about!
They may be persistent because you've never responded to them. (The "friends" may be "Friend" requests from people you knew years ago who've tracked you down.)
FB is insidious as far as data collection and correlation goes!
I once got a "Friend" request, and at the bottom were the names of three people "
you may know", and I
did know two of them, and there's no known connection or link between any of the "befriender" and the two people I knew. The episode scared me away from FB forever. (I clicked on the included "Never darken my doorstep again!" link.)
That was my one and only FB experience, although I'm certain that they've got a record of every public page I've ever looked at, albeit attached to my ISP address, not my name.
