There are quite a few videos on YouTube where the owner (I assume, via an alert that the motion sensor is triggered) starts speaking though the device remotely "put that down" or "get out of here" and the would-be thieves usually drop the package and hurry off.

EDIT: I should add that a video circulated recently in my neighborhood showing someone stealing the camera. So there's that risk. I'm sure the thieves will be disappointed when they find out about the monthly fee.