As I was looking through the functions of my new D3, it occurred to me that since it's effectively a pretty sophisticated computer, that you could have an optional, user-selected function that would pop up every so often at the user's direction (like every fifth or twentieth time a card is inserted) that would require the input of a password -- maybe, say, a ten-letter password. After the ten-letter password is failed x number of times (like 5), you'd have to go on-line with the company's website, and provide them with the answers to your secret questions before you'd get the function back.
Of course, you could also opt to simply turn the lock-up function off.
But if you turned it on, while traveling, you'd have the satisfaction of knowing that a thief and whoever he sold the camera to would not get more than x number of actuations off the camera, and if they called the company or went to a repair shop to get it fixed, the police could be notified or whatever. In any case, the camera wouldn't work. If there were a subtle built-in hardware code reader for this (something like a dongle) it might be hackable, but the hack would probably cost as much as a new camera, and the first guy to hack it would have to destroy his $5,000 camera to get at it...
Punching in the code would be a pain in the ass, of course, but if you did it at the minimum that you knew you could stand, it'd be okay...
Also -- I'm just thinking this up as I go along -- you could have a little padlock symbol that showed up the LCD, and after this kind of lock-up became known, a potential buyer could look at the LCD and if the padlock was there, he wouldn't buy it from the thief; so it would become known that the cameras weren't worth stealing.
JC