One frightening aspect of an intelligence computer is that it could program itself. If man built the machine, and the machine is about as intelligent as man, then the machine must be capable of understanding and thus improving a copy of itself. When the copy is activated it would be slightly smarter than the original, and thus better able to produce a new version of itself that is even smarter.
This process is exponential, just like a nuclear chain reaction. At first only small improvements might be made, as the machine is only just capable of making improvements at all. But as it became smarter it would become better and better at becoming smarter. So it could move from being barely intelligent to hyper intelligent in a very short period of time.