Yeah, I have a strapped on rack too. I lock the bike to it, but as my LBS guy and aka_kim pointed out, that only adds a step to being ripped off. So I rarely leave the car w rack and bike at all or for more than a few minutes. Luckily I'm still w entry level bike. I'd be PO'd if it was stolen but might have recourse to buy a better bike. Of course that would leave me w/o a decent bike for weeks.
Does anyone feel weird too a bike rides just laynig your bike down and walking away to use the porta john?