So let's talk locks and security

I thought a wheel is under so much tension from the spokes that a saw would get jammed trying to cut a rim. Wouldn't a bolt cropper also struggle with the tension?

No. Obviously not.

A bolt-cutter doesn't have a sawing action. It would snip the spokes like cutting paper with scissors, and once the tyre is removed, the rim would cut easily.

As for Edscoble's saying that a bike thief wouldn't want the hassle of trying to find a rear wheel to resell a bike - I disagree. The thief could simply sell the frame. Then swap the parts with other stolen bikes. Most professional bike thieves would have MANY rear wheels from other (maybe less expensive) bikes they could substitue with.