While I admittedly have not been a great fan of Bing, I do concede that including Tweets in search results can be a potential game changer. It could spell a greater challenge to the concept of searching information via a huge cache of indexed pages
While Google could easily pull a switch and include real time content in it search results, but then this is the first time when Google will be seen catching up on innovation.
Historically Microsoft's definition of innovation has been copying competitors and coming out with something better. I guess this time Google may have to follow Microsoft model of innovation