IMO, google really left yahoo. it's hard to explain far behind yahoo is because of all the applications that google had developed. i don't wanna say anything bad about yahoo or something that might lower the reputation of them but we ourselves, webmasters, can easily compare how better google really is when it comes to web applications.
Well I guess, Google and Yahoo are the top 2 search engines today though Google offers new technology and they almost sets new standards for search engines because of their innovative ideas... I think Yahoo is not that far behind. Yahoo is still very popular... we can't erase the fact that Yahoo once conquered the net. haha