Assuming that by "AI" you mean something that maximizes a utility function, as opposed to a dumb apocalypse like a grey-goo or energy virus scenario.
I can see how a “dumb apocalypse like a grey-goo or energy virus” would be Artificial, but why would you call it Inteligent?
On this site, unless otherwise specified, AI usually means “at least as smart as a very smart human”.
http://www.youtube.com/watch?v=ghIj1mYTef4