An interesting article by Amit Singhal of Google, explaining the technology that figures out what you mean, as opposed to what you say.
Most users have used our spelling suggestion system at one time or another. It knows that someone searching for [kofee annan] is really searching for Mr. Kofi Annan, and is prompted: Did you mean: kofi annan; whereas someone searching for [kofee beans] is actually looking for coffee beans. Doing this internationally with very high accuracy is hard, and we do it well.