A male friend who uses you to meet women and becomes their friend on Facebook. They accomplish this by hanging out with you in casual settings (ie. bar/festival/party). When you bump into or meet up with female friends he will latch on to her/them by using Facebook. He's very unsuspecting and he does it in secret while you are in the bathroom or distracted in another conversation with someone else. He will approach her innocently and say something like "Hey, are you guys friends on Facebook? Can I be your friend too?"
He will do this with your current girlfriend, ex-girlfriends, or long time female friends.
Ways to figure if your friend is Face Leech:
1. Hang out with him at a bar till you accidentally bump in to a female friend. Next morning, check to see if they are friends on Facebook. If they are friends and you seemed to have missed the conversation about them being friends on Facebook... Your friend is probably a Face Leech.
2. Look in your mutual friends with him. If its all girls and just another guy or two... He's most likely a Face Leech.
Dude, Bob and I were hangin at the bar and accidentally bumped in to my ex-girlfriend Kristin... and now their Facebook friends!?!?!?!? I hope that Face Leech isn't' trying to go for sloppy seconds!