Some random musings:
* Around here -- where bike thieves are numerouse, skilled and knowledgeable -- thieves have been known to cut through the frame to steal a bike with nice enough components. The rear wheel is nothing in comparison.

* A while back I threw away a ruined wheel. I easily broke the rim into pieces using my hands and feet so I could fit it in the trash can.

* When I bought my bike, the guy at the store made a big deal of showing me Sheldon's technique. Except he advocated not running the u-lock through the frame at all, just through the rear wheel. I say that's nuts, the weakest link is then the rear rim, which can be broken easily. I put a U-lock on the front wheel and the frame, and a cable lock on the rear wheel, frame, and seat.