I would guess it has something to do with your IP address that they can at least trace a general area for you. The scarier stuff is if you google your full name. There are sites out there that collect personal info on people. You can see general stuff just by clicking on a person's name. Give them a few $$ and they'll provide a bunch more info. I was on one site that provided my address plus you could click a link to get directions to my place. I opt out of those sites whenever I find them. I can see no reason that personal information should be online and so easily accessable.

Andrew