pity friend
n. On a social networking site, a person whose friend request you accept out of pity.
Other Forms
Consider paring down your Facebook friends to ensure that personalized search results are as relevant as possible. (No more pity friend accepts!)
—Laurel Miltner, “Picks of the Week: May 16-22,” PR 20/20, May 24, 2011
Do you hate Facebook's new design? Do you find the home page too noisy, with important updates from your friends getting buried under a stream of banal comments from high-school classmates and other people you pity-friended?
—Farhad Manjoo, “Stop Whining About Facebook's Redesign,” Slate, March 23, 2009
2006 (earliest)
two weeks later, i now have two friends on facebook (the other one is scott, who made me a pity friend).
—Henri Jacques Suermondt, “social,” Suermondt.com, August 07, 2006