I'm continually amazed when I see the statistics on what gets stolen, at least here in LA. You might think that the expensive cars would be the main target, but that's not really true. The main targets are hot muscle cars, stolen for joyriding; cars that are known to be easy to steal; certain cars with unusually expensive parts; and things like that. I'm also surprised at how easily thieves can be dissuaded, by even the simplest precautions.
My own example is my 86 Toyota van, with a spare tire that was expensive and easy to steal. Thieves tried to get it FIVE TIMES in the first couple months I owned the car. They popped the catch, discovered it was chained on, and left. Could easily have cut the chain with bolt cutters, but even that little complication stopped them. Finally, I got smart and arranged the chain so it was visible at a glance--never again did anyone try to get the tire.
So, my suggestion is to view anything as a theft target, take simple, reasonable precautions to protect it, and probably you'll be OK.