http://en.wikipedia.org/wiki/Anti-spam_techniques_(e-mail)
"3. Leaving messages on the spamvertised site. Spammers selling their wares need a tangible point of contact so that customers can reach them. Sometimes it is a telephone number, but most often is a web site containing web forms through which customers can fill out orders or inquiries, or even "unsubscribe" requests. Since positive response to spam is probably much less than 1/10,000, if just a tiny percentage of users visit spam sites just to leave negative messages, the negative messages could easily outnumber positive ones, incurring costs for spammers to sort them out, not mentioning the cost in bandwidth."
Eli, jos tulee roskapostia, käykää viitatulla sivustolla ja antakaa negatiivista palautetta. Jos kaikki tekisivät näin, niin spammaajan oma palvelu menisi tukkoon jo yksistään negatiivisista palautteista. <xD>