This article comes courtesy of the Literary Minded blog by the awesome Angela Meyer, regarding the etymology of ‘Unfriend’. David Crystal writes:

In 2009 the New Oxford American Dictionary chose unfriend as its Word of the Year. It meant ‘to remove someone from a list of contacts on a social networking site such as Facebook’. A minor controversy followed.

Check it here: http://literaryminded.wordpress.com/2012/01/02/etymology-monday-david-crystal-on-the-word-unfriend/