Most thieves want to ride the bike away. Removing the front wheel helps deter them. There is still some risk, but it is lowered.

I agree that a folding bike (that can be taken with you) can solve some of these problems.

Also, there are bike lockers available in some areas, and some parking garages have secure areas for bikes.

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This may be worth knowing about: I once found a beautiful, very high-end, handmade steel frame with a stunning paint job, that had a section of tubing (approx. 3") missing from the seat tube. The bike had been stripped, and the frame had been ditched.

That's another way to defeat a lock.

(Sometimes I see several u-locks still locked to something, all alone, with no bikes. I wonder how many of these have been defeated by cutting out some portion of the bikes.)