This afternoon, Bing will take a big step forward in terms of social search. Yusuf Mehdi, Senior Vice President of the Online Audience Business at Microsoft, announced at SMX Advanced that a Bing site will start to integrate information from Facebook. Bing.com/social - which isn't live at the time of this writing - is supposed to build on the connection Microsoft has been establishing with Twitter over the past year or so. And indeed,