Can they be easily stolen?
It looks like they are not "securely" mounted, that they simply stick to the wall via magnet. Could someone just grab them and walk away?
Yes, they are simply hooked up by a strong magnet. If you can't install high enough to avoid theft, consider buying an Arlo skin cover which helps camouflage the camera to its environment. I had to buy a brown one for my porch. Unless you know what your looking for the average person wouldn't see my porch camera.