Messing with the cops for no apparent reason is generally something one should advise against. There are a lot of things that make this statement true - tazers, guns, and ultimate control of your freedom, just to name a few. These guys decided to screw with the police by making them get out their cars for absolutely no reason.
I'm not sure if this is funny, an exercise in civil disobedience, a protest against all of the recent examples of police brutality, a demonstration of having pretty big balls, or just douchey. Whatever it is, I'm shocked that the officers were all so cool about this. You'd have to think that one would at least feel the need to smack one of these punks across the back of the head.
Then again, it is pretty clever. Warning: Do not try this at home, as you have no idea how accommodating the police in your town may be.[h/t Fark]