The AirTag has a anti stalking mechanism, so than when an unknown AirTag moves with your iPhone you will get a notification.
This would mean that a thieve with an iPhone will get notified that the stolen item is being tracked. The thieve can locate the AirTag with his iPhone and disable it.
So for theft situations the AirTag seems to be pretty useless to me.
Am I missing something? Is there a solution to this built in?