Contact scraping is the practice of obtaining access to a customer's e-mail account in order to retrieve contact information that is then used for marketing purposes.
The New York Times refers to the practices of tagged.com, mylife.com and desktopdating.net as "contact scraping".
Several commercial packages are available that implement contact scraping for their customers including ViralInviter, TrafficXplode, TheTsunamiEffect.
References
Contact scraping Wikipedia(Text) CC BY-SA