I work in a large downtown area where a lot of bike thefts occur in our city. The vast majority of criminals that are stealing the bikes here are addicted to meth and thus are stealing them and trading them for dope, or changing their appearance by spray painting them changing out parts and then riding the bikes themselves for transportation (getting around town to buy/sell more dope). They almost always carry a set of large bolt cutters in their backpacks so the U locks are one of the only types of bike locks that actually prevent them from being stolen.. Most of the cable locks, chain locks, etc. are not even the slightest deterrent to these types of thieves from stealing someone's pride and joy. I suppose a cable lock will prevent the opportunistic criminal that's just looking for an easy boost, but for the professional thieves that are actively hunting bikes to steal, you'd better have a cable lock on it or better yet, have your bike in your possession at all times (in these types of areas). It amazes me how many people don't actually record their bike's serial numbers down as well, just in case the worst scenario does actually happen and it gets stolen. There's been dozens and dozens of bikes that I've seen criminals using that I absolutely knew were stolen, but sadly the owners hadn't recorded the serial # down, and thus didn't have the # when they reported it as stolen. I've seen some of these criminals breaking down a stolen bike, swapping parts out, and spray painting them in mere minutes! It's like watching a NASCAR pit stop. Sad.