Around here, phone popularity has a lot to do with what would get stolen. I've NEVER seen another N900 and I live near Chicago. You know what I do see? iphones, Droids, EVOs... thats the stuff that gets stolen.
Thieves steal things that are valuable, but common, so they can sell it easily. Thieves busted into my friend's car and they stole his ipod nano. He had a $1,000+ camera lens in its branded case in the backseat... it was still there when he got back.
But if I was stealing a phone, the first thing I would do is to pull the battery.