Are you blocking Flash Cookies?
Spammers and people without regard for your privacy or your privacy preferences (blocking cookies means I don't want them in any form) are insidious.
Unbeknownst to many people, Macromedia Flash player allows surreptitious cookies to be dropped on your computer that can be used to track you even if you block traditional browser cookies.
Some information on eradicating them:
Firefox extension for blocking flash cookies:
[http://www.yardley.ca/objection/]
Macromedia info (opens up the hidden flash config tool in your browser that lets you view and expunge flash cookies):
[http://www.macromedia.com/support/documentation/en/flashplayer/help/settings_manager06.html]
EPIC Flash Cookie page:
[http://www.epic.org/privacy/cookies/flash.html]