BTW, I also disagree with Mr. Allen's advice to take a wheel or saddle and seatpost with you when you leave the bike. An incomplete bike looks like an abandoned bike, and real world experience indicates that gives a green light to others to
strip its other parts as well.
That's a really good point! I'd never thought about how the broken window theory applies to bicycles, but I would definitely believe it.
I've become fairly lackadaisical about bike security around Calgary. I have yet to lock up my Brompton for more than half an hour or so, but I will probably end up doing so to go to a bar where it's too crowded to bring it in. Somehow I feel like I own unique enough bikes that, if one were stolen, the thieves would have a tough time selling it without me finding it, at least locally.
I use a chain lock, the kind that's wrapped in nylon. I think it's a pretty good compromise between U-lock security and cable flexibility, though it's probably heavier than both.