From the Official Google Blog:
It all started with tarsorrhaphy, a rare surgical procedure on eyelids. In the summer of 2010, we were looking at the search results for an unusual misspelled query [torsorophy]. Google returned the correct spelling - tarsorrhaphy - along with results for the corrected query. At that time, Bing had no results for the misspelling.
Later in the summer, Bing started returning our first result to their users without offering the spell correction. This was very strange. How could they return our first result to their users without the correct spelling? Had they known the correct spelling, they could have returned several more relevant results for the corrected query.