Bing has the upper hand with those signals coming from Facebook while Google is still Google, and is still the search engine of choice worldwide, regardless of what signals they have or don’t have.
My question is not so much about who will win this game. Google is the 800-pound gorilla that Bing has to move in some direction so it can make any progress. That alone is a daunting task.
However, add into the mix that Bing actually already delivers better results (in many opinions) on certain searches that go beyond the blue link text results and you can see that this mountain is about more than a better service.