It's easy to lie with check-in based social location sharing utilities like Brightkite, Gowalla, and Foursquare. I've used them all (though recently have lost interest). With each I can fake my mobile location at anytime, and sometimes I have when in a punchy mood. There are measurable social implications to this - that is making lying easy - supporting a moral decay killing local trust, particularly in the US. That's a heavy academic topic, and I don't want to got there today.
Clearly, he's a cheater; exactly the kind Foursquare must want. After all, the more he fibs, the better Foursquare's POI database gets. I have no interest in helping Foursquare build a POI databases for their benefit, particularly when there's none reciprocated other than bragging rights shared amongst a user community all doing the same.
I'll keep using Latitude. It's incapable of lying, mostly importantly, to myself.