The fine folks at BugMeNot (free registration required) are sponsoring “Internet Advertiser Wakeup Day.” I think it’s a cool, but flawed, idea. If you believe that paying for service is better than kneeling before the advertisers and giving up your privacy, then poisoning the databases is good.
However, to be effective, the poisoning needs to be slow and pervasive. If it all happens on one day, they can throw away that data. If it all happens over the course of a month, throwing away the data gets more expensive.