TechCrunch's MG Siegler:
KrazyDad was a man on a mission: to show the holes in Foursquare’s check-in based system. And boy did he.
To be clear, anyone who has used Foursquare quite a bit is likely well aware of these holes. For example, there is nothing to stop you from checking-in anywhere in the world you want except that it’s easier to do it at a venue close by that automatically shows up on your list. But this guy, KrazyDad, used Foursquare’s API and some scripts to do his dirty work. In the end, he had captured dozens of mayorships across a range of fake Foursquare accounts.
This was less a problem when only a few San Francisco dot-hipsters were on Foursquare, but now with some businesses offering deals or discounts for mayors and other top users, cheating is a real problem that'll have to be addressed.