There was a fellow on another forum whom I advised on buying a Dutch-type commuter bike, which he intended to use for four seasons commuting -- in Chicago! Of course, he was nuts; I spent a winter in Chicago on exchange when I was a student, and thought it was a stupid place to put a city, and bloody dangerous even back then, even though I lived in an apartment block with security; but he was divorced and alimony just didn't leave him money for a car or living in a safe area, so he had no choice.
His bike was stolen shortly after he bought it. He reported the theft to the police, complete with an address where his bike could be found. The cops basically told him they were busy, so bugger off. But one relatively helpful policewoman explained to him that the cops couldn't be bothered with arresting thieves because the thief would just say the owner gave him the property, and the court would let the thief go.
I told him to hire a couple thugs off the street and fit them and himself up with steel twist-out trolley handles from the trolleys used to push heavy loads of paper around the printery where he worked, and go recover his bike, arranging with his own thugs beforehand to all tell the same story, that the thief resisted.
About a month after he got his bike back and thanked me for my advice, he dropped me a note to tell me an odd thing. Apparently one of the women in his apartment block came up to him on the street and without further ado kissed him on the cheek, and thanked him for making the block street safe for her children.
His message was on a postcard, of which he'd printed 1000 at work; the illustration on the card was a photo of the bike thief walking on crutches with his legs in plaster, which he distributed in his neighborhood. He claimed that his association with me had proved illuminating...
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Of course, I don't normally beat up thieves, mainly because there aren't too many where I live. But I instead make my bike impossible to steal with an
n'lock (sic, all lower case) system, which when I park the bike uncouples the steering tube from the handlebars, much like a car steering lock, but in reverse. Anyone who grabs my bike and jumps on impetuously will immediately enjoy a faceplant.
You can read about experience with the n'lock on this forum at
http://thorncyclesforum.co.uk/index.php?topic=3930.0 -- I really couldn't imagine being without it, and other members who fitted one tend to agree.