CB long : The program I use (Ad aware) detects what they call spy cookies that track where you go on the net & then the collecting agency sells that data to commercial interests who will then spam you with stuff they already know might interest you.
The Ad aware program also identifies the source of the cookie implants which include the following, " valueclick" " doudleclick"
"ezula" "gator" etc etc etc .
I recently updated to version 6 which found an additional 160
cookies & deleted them.
I visit a lot of motorbike sites & suddenly I got spammed from Harley Davidson !!!
Not any more.