spammer's paradox

Spamming itself may be defined as the abuse of electronic messaging systems, cybernetic or otherwise (including junk faxing, for example), for the purpose of sending unsolicited bulk messages. In order for spamming to succeed, a disproportionately large quantity must be delivered successfully to its recipients, or there will be an insignificant return. Unfortunately for the spammer, it is exactly that large quantity that renders any individual piece of spam less effective: the moment a large enough number of the same piece of spam is sent, the message becomes identifiable as spam by anti-spamware, forcing the spammer to start from scratch with a new spam tactic. This is the so-called "spammer's paradox".

Good example: the mass E-mailing of online pharmacy advertising created a spammer's paradox in many large corporations because it only took two instances of the same spam reported to their IT departments for the spamblocker immediately to delete the rest.