social leach
One who burdens the grace of others by gaining invitation to social gatherings for which the social leach is not equipped to contribute but will still make partial gains at the expense of participants who believe they are benefiting the social leach by being nice to him or her which causes a continuous blood supply from which the leach can suck as he or she achieves more unwanted invitations.
The social leach listened in on all my conversations at the party despite the fact that I ignored him all night, but no one had the balls to tell him he isn't invited to the next meetup.