Many of the game sites tag that stuff onto you, esp if you don't use a pop up blocker. Then, if you click on a pop up ad, you're in the tracking for sure.

Also, many sites like for ecards and such have an agreement you click off before you can use the site, and few ppl actually look it over. OFTEN you can scroll to the bottom and find a place where it's automatically checked off for you to receive third party emails and in essence, spam. Unchecking the box stops a lot of that.

TC