Someone who is obsessed with Facebook (usually a girl) it is rare for them to be offline. Facebook-Whores usually have a Facebook app on their phone, so they can easily check newsfeed, create new status's, add pictures ect. They usally don't have anything to do besides look at random peoples pictures, info,wall ect.
Sarah: "Mary is such a Facebook-Whore!"
Emily: "I know! She is always looking at random peoples stuff.."