I'm not superstitious at all, but I also thought black cats were supposed to be unlucky.

All superstitions most probably date back to a stupid incident happening to someone (like walking under a ladder and probably got paint on themself), and it escalated so everyone knows them, but they're all a load of crap.

The only way any of them would work out to be unlucky is if a person (for example) saw a black cat, and then believed that something unlucky would befall them, so they do everything that day pessimisticly (sp?), and if something even slightly misfortunate happens to them they think it was because that one small, insignificant thing happened.