Some sites actually use gender based advertisement.
If you tell the site if you are male/female
and your age...
it will generate advertisements that suit your demographic.
So if the 21 yr old male logs into said site, he will see a hot chick wanting to sell him something that he doesn't need.
this is another reason why T.V. is just going to go the way of the 8 track...the CB radio...and the Dodo bird catching device.
It gets even more sophisticated than that even.
If your protection systems are lagging, tracking info can get quite extensive. They can pin you down to a 26-year-old croat-mexican living on topeka kansas with an xbox what games it has and whether or not you like tapioca.
Whats the moral then children? Erase the godamn cookies. Preferably before somebody raids that treasure trove of credit card numbers you didn't realize was there.