Once in, the same factors, (plus the resonablility of your prices, maybe display, advertising, ect?) would influence an npc's decision to buy or not.
Stolen goods could have a chance of being recognized and you reported too, a high chance if it's a guard, and a very low one for civilians. (sneak and security could influence this percent too.)
Maybe even have some random events of thieves breaking in. Sure would make things more interesting.