Seems like it might actually be better to let employees run free, and just keep a mild watch out. That way, any employees with unethical/stupid tendencies to do things like steal office equipment and resell it will make themselves known rapidly, rather than potentially festering and worming their way into a position of trust before betraying it on a much larger scale.

I don't think stealing is the biggest concern. The implications in terms of firm culture are more damning than the actual act itself.

I'm not saying you make it easy so you can catch thieves and avoid having your stuff stolen. I'm saying you make it easy because, I figure, less ethical people are more likely to steal, so it lets you weed out bad people in general.