Microsoft used to be able to "embrace and extend" in order to extinguish the competitor. With Bing it seems they can only "embrace", by which I mean copying and trying to decrease differentiation. But look at the trend. In the future, when/if Google search incorporates social feedback effects (ala +1), Bing won't even have the user-base to be able to copy the competitor, let alone extend and extinguish.

One look at my website statistics tells me Bing is already as good as dead.