Casey Neistat tries to steal his own bike in several locations around NYC and finds out that it wasn't hard. He even does this right in front of a police station:

I recently spent a couple of days conducting a bike theft experiment, which I first tried with my brother Van in 2005. I locked my own bike up and then proceeded to steal it, using brazen means -- like a giant crowbar -- in audacious locations, including directly in front of a police station. I wanted to find out whether onlookers or the cops would intervene. What you see here in my film are the results. I would guess that this may be easy to do in most large cities, what with out apathetic most pedestrians are to what is going on around them.