I noticed recently that both major style guides' preferred dictionaries advocate the spelling "doughnut."
Merriam-Webster, which is followed by most book publishers says that "donut" is a variant spelling of "doughnut." Translation: Down with "donut."
Webster's New World, which is followed by most news media, says that "donut" is informal for "doughnut." Translation: We're down with "donut," too.
But the masses, it seems, beg to differ. Doughnut gets about 6.8 million hits on google. But donut gets about 9,830,000.
Usually, I'm pretty awed by lexicographers and how well they do their job. But every once in a while, I just gotta poke holes ...