The Wikipedia description of a stack overflow should probably be the best link and it ranks 5th.
That would be my thinking. Ok so maybe wikipedia doesn't have to be the top result, but I'd rather have results relating to the thing I'm searching for come above sites just named after it.
I'm really just expressing a preference :)
"define ford" shows a dictionary definition of ford before all results, "define stack overflow" shows a link to wikipedia before all results.
Of course with the imprecise and constantly moving nature of language this is not easy.