I notice an interesting phenomenon of organic ranking in Yahoo and Bing. Yahoo and Bing alternately shows my organic ranking for a couple of keywords. Sometimes it just doesn't show up on one, but does for the other, and vice versa. Is it because my keywords of photo to portrait, portrait from photo, portraits from photos are not strong enough? Or it is Bing and Yahoo's algorithms are supplemental to each other?

Bing and Yahoo merge their paid ads service. Do they have certain tacit agreed algorithm on organic search and ranking. 

I will find out answers in coming future.