There's a theory that toxoplasmosis, given it can transfer from cats to humans, is the reason for the 'crazy cat lady' stereotype. Certainly, cat owners I've known seem more likely to have 'attacks' of extreme aggression than the general population, and giving vent to that does seem like a 'risk' to our status in the community that most of us don't take. Then again, having that sort of temperament may make someone more suited to owning cats than other pets...