said by Pirate515: said by KrK:
We'll keep it, thanks...
I don't think that any sane store rep would be willing to attempt to take the phone away, especially from a thief. Refusing to activate would probably be as far as any carrier would be willing to go. Now, if they hand it over voluntarily, I don't see any reason not to take it. And if that be the case, as an act of courtesy, the carrier should try to contact the rightful owner to see if they want it back.
As some have already pointed out, the primary purpose of this system is not to punish thieves, but to discourage them and thus prevent cell phone theft. If they know ahead of time that they can't use and/or sell a stolen cell phone, maybe they won't bother stealing it in the first place.
The store should be required to call police and report anyone trying to activate a stolen phone. If the police say, "We are too busy" then let the guy go without activating the phone. When the crackhead sells it for $10, the next idiot will come in and then get arrested for possession of stolen property.