I was just sitting down to write this, when my doorbell rang. It was a young man who said he was a locksmith and needed a place to plug in his saw to saw the lock off a bike parked in front of my house.
I decided I should be responsible and ask for ID, and he was willing but also called over the owner of the bike, who was someone I'd seen going off for a day at the beach with one of my neighbors.
It took the locksmith a good 15 minutes even with power tools to get the lock off, which speaks well for how secure Kryptonite bike locks are. Kryptonite had also told the owner that they'd replace the lock for an $18 fee, if she sent them back the pieces.
She said that she'd lost all her keys, but getting into her house hadn't been a problem -- she just went in a window. And then she had a duplicate key for the house, but hadn't had the second key for the bike lock for some time.
So there are good urban neighbor stories.