Bing appears to have been piggybacking off Google’s results. Considering Bing historically sucked at serving long tail results, it’s no surprise to see them do whatever they can to return more relevant results. I can’t decide if this is simply a brilliant use of competitive intelligence or laziness, or both.
Other non-search perspectives from Nate Silver of the wonderful political blog 538 (notes how Bing’s “It’s one of 1,000+ signals we use”, is bogus) and Barry Ritholtz from The Big Picture (says Microsoft has always stolen) are worth a read.