Really? Have you been asleep lately? Did you miss all the announcements that Bing are now supplying Yahoo!'s search results.
you're right.. yahoo and bing joined forces on supplying results that is why there are plenty of times wherein if you search on both SE the results are similar..
Yahoo and bing both are totally different, yahoo is very old search engine where as Bing is new search engine its services. features are not so much good.
have you been living on a different planet? Did you miss you all the discussion that Bing is now powering Yahoo's search results? Did you not notice the 'powered by Bing' on Yahoo's search results? You need to stop posting crap that misleads people.