professional bike thiefs will get your bike if it is worth it and they want it. But the real worry comes from young and homeless people who will just jump on an unlocked bike to get somewhere when they are walking.

I always lock my bike, mostly i dont want to get stranded without a way to get back home. I have about 15 riders,,,if somone asked me for a bike I would give it to them and have given away about 50 bikes.