how does evil bob do this?
evil bob drives the country in a 1973 Ford Econoline - living off of Vienna sausages, Funyuns and Mountain Dew - looking for Foursquare users who have made their home addresses public.actually, since evil bob doesn't actually exist, that's not true. there's a guy - we'll call him Ken - who cobbled together little bits of internet magic to bring evil bob to "life".
evil bob looks for tweets from foursquare users that seem to be "this is my house" sorts of check-ins, then he follows the link. if the "venue" appears to be an actual address (or very close to it), evil bob checks in there himself. and that sets off a chain reaction that leads to evil bob's location (i.e. somebody's house) being automagically reposted back at foursquare, tweeted out as evil bob's own check-in and presented here - with a handy map. evil bob could also look for venues at foursquare called "home" or whatnot to find places to visit, but he doesn't.
evil bob isn't trying to catalog every instance of foursquare users publishing their home addresses; he's just trying to make a point. so there's not a script that checks tweets; that's done manually. plus, the whole evil bob thing went from a concept to a live product in two days; so there was enough scripting and development in the updating part to worry about without getting into some deep automated psychoanalysis of tweets to determine what is a real address.