My wiew on artificial intelligence

Resident Evil, Terminator 3, Matrix and now Stelth, just to mention some of the popular movies. Why does an A.I. that becomes self concious have to be evil, start chasing and killing people and so on? Obviously the idea is more comercial then a supercomputer that starts doing good stuff. However, there is certain withheld on all levels regarding this issue in real life. It might be our usual fear of the unknown.
An artificial intelligence may be more or less smarter than we are. If is less, we should be able to control it, if is greater then us, then there would be no problem in letting it guide us and we may really need that someday. But I am optimistic :). Actually I like this issue, maybe I'm gonna work on it some day.