They are great at the Woodward Dream Cruise because its a horrible traffic jam that bikes can squease right through, but then again, motorcycles can do the same thing better. I suppose its a community policing move (if I'm using that term correctly), and a move that makes far more sense in a big city than in a little town. Many people hate and fear cops and bike patrol officers seem to dispell some of that. Plus bikes are obviously cheaper than a fully outfitted squad car.
Only problem is bikes can't get anywhere fast, and they can't hold a lot of equipment.