I think you have to consider the matter from a Bayesian perspective before just labeling it as "for paranoid loons". If I behaved this way in my environment, I would pretty much be being a paranoid loon. On the other hand, if I were riding the New York subways every day, it would be nice if there were at least a few civilians keeping an eye out for things. (Not everybody, though; that's a recipe for hundreds of false positives.) There are other people who aren't being paranoid loons, like researchers who use animals; for them this is a real concern.