Just to tell a real-life story illustrating this point:
I was AAAI '98, in Madison, Wisconsin -- the big Artificial Intelligence conference. They had a demonstration hall, where they were demonstrating AI technology. They had a demonstration where Many Faces of Go, one of the world's better computer go players was up against a 3 dan American professional Go player (3 dan is pretty good, but not stunningly good. Probably compares with a chess Master, with a ranking of 2100-2200).
First he played it with no handicap. He walloped its ass badly.
Then he gave it a 9-stone handicap. This is a huge handicap. A beginning player who's been playing intensively for 3 months can beat a 3 dan player with a 9-stone handicap.
He still kicked ass.
Finally, he played it with a 17-stone handicap. A 17-stone handicap is unheard of; I mean people don't know where to put the stones with a 17-stone handicap. This time he had to work a little harder, but he still won. And he wasn't even bothered, nor did he take long to analyze moves.
It was incredible to watch. A potent reminder that artificial intelligence still has a long way to go.