While I don't approve of some (most?) of their antics, Phone Losers of America did a series where they "prank called" users of Foursquare and started reading of

While I don't approve of some (most?) of their antics, Phone Losers of America did a series where they "prank called" users of Foursquare and started reading off details about their personal lives. Pretty scary stuff that puts things in perspective.