Google already does this. I saw an interview with Matt Cutts about a year ago and they even gave specific examples of how different results were generated using the same word in two different contexts.

Of course, MS lives on the 'embrace and extend' philosophy where they embrace successful ideas and extend them with proprietary and secret code which ends up relying on other MS stuff to develop or work. But I would be surprised if they manage to pull it off, after all they have tried again and again to get search working, with live being their last of many mediocre offerings.