Those pesky theives

Have you been robbed of your merchandise or haven't been paid for some borrowed merchandise?
There isn't much you can do without using violence. Violence is essential into striking fear into these people. It may be the only way. To avoid these problems don't get caught up in it in the first place. Stick with people you really know. Not a friend of so and so. If you truly know them, the chance of being robbed is significantly decreased. Also the chances of dealing with a narc is decreased.
Make it your priority not to let people borrow merchandise on tab. If they don't have the adequate funds, they don't get anything until they have the cash. If they don't have the funds in the first place, it may be an obvious sign that it will be difficult for them to acquire it. This is true for most but not your most trusted friends that always pay their tab. If you think about it, you are in fact losing business. Keep tabs on who pays up and who doesn't.