To remove a 'friendship' from facebook due to having either accidentily adding him/her as a friend or actually adding them and reconsidering later.
"Yeah, there was this guy in my network who added me. I thought he looked ok, but his updates were really cramping my news feed, so I had to deface him."
"I went on a date with a girl I met a week before and like the day after our date she changed her status to 'in a relationship.' I defaced her."
When the news feed in your Facebook home becomes clogged with meaningless updates on people's lives (e.g. Jim is now flossing his cat).
"Man, I logged on yesterday and Jim was really giving me news cramp. He changed his status about 5 times!"
"This girl I added last week must be on Facebook all of the time. I got some serious news cramp from her. I think I'll have to deface