Quenqua, Douglas. "Friends, Until I Delete You." New York Times 29 January 2009: E1+.

Quenqua reports on the recent "Whopper Sacrifice" advertising campaign (if you unfriended someone from your Facebook, you would get 1/10 off of a sandwich during your next visit to Burger King). The bulk of the article focuses on Facebook's friend feature - did you know that if you are unfriended, you will receive no notification? Interesting stuff if you like to think about online social networks and social relationships.