square stalker
Using Foursquare to see who has checked into the venue you are at, and then looking around to try and find them.
Square Stalker: *shows friend picture from Foursquare profile on phone*
Normal Friend: What?
Square Stalker: This person is here. Do you see them anywhere?
Normal Friend: Dude stop square stalking, weirdo.
Normal Friend: What?
Square Stalker: This person is here. Do you see them anywhere?
Normal Friend: Dude stop square stalking, weirdo.