People don't like security guard robots that look like security guard robots. There's an easy answer to that: make it cute. I don't have any hard numbers, but I

People don't like security guard robots that look like security guard robots. There's an easy answer to that: make it cute. I don't have any hard numbers, but I'd be willing to bet people are much less likely to vandalize a robot that looks like Wall-E than one that looks like ED-209, even if they do exactly the same thing.