Individuals who have anyone they've ever met in their entire lives added as friends on their Facebook account, particularily members of the opposite sex.
"Did you see Bob's friends list on Facebook? He has like 700 friends. Wow, he's such a faceslut!"
A combination of the words Facebook and slut. It pertains to a person who over uses Facebook or a similar social networking site. Some one who posts too many pictures or comments on other's (or worse their own) pictures. Someone who updates their status 25 times a day or someone who spams others with useless invites.
"I am so sick of getting Sally's invites to these fucking stupid public action groups, why is she such a faceslut"