Another reason to not install Flash in your web browser (or, at least, switch it off and start it manually when you need it); not only is Flash used primarily for making ads more annoying, but now it can
bypass cookie privacy controls to keep track of your web-browsing habits. (via /.)
Macromedia have a page where you can access your Flash plug-in's privacy settings; if you're using Firefox, you may also want to install Flashblock, which disables Flash by default but lets you load Flash applets on a case-by-case basis.
thanks for the tip palleyroo!