I believe this move is to counter-act Google's announcement of their tighter integration of social search elements into the search results.
With Google, these social integrations can influence the ranking of the results - it does not appear to be the same with Bing's Facebook integration. It seems that if a Bing search result does have any Facebook like data, then Bing will label it under the search result. Bing will not boost a search results in the rankings based on that data - at least not yet. Also, Bing has Facebook likes, whereas Google does not.
Here is a before and after screen shot of Bing displaying such results with Facebook likes:
Before - Bing Without Facebook Likes:
After - Bing With Facebook Likes:
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