As announced but as expected and seen already, Bing is, on occasion, powering Yahoo results - so they can test Bing powered Yahoo results in the live results.
You have a pretty good chance of seeing Bing powered Yahoo results. As I mentioned at Search Engine Land, up to a 25% chance of seeing Bing organic results on Yahoo. And for the first time, I personally see them matching. Here is a screen shot, side by side, showing them matching exactly, even the images:
The red portion is the only portion of the "organic" section that is not the same. Why, well those are not really "organic" results, they are news injected results.
The Bing Search Blog also posted this morning, emphasizing:
For webmasters, it’s important to be familiar with how the Bing crawler interacts with your site. After the full algorithmic transition is complete, you only need to optimize for one crawler (Bing), as we will provide Yahoo! with results from our index.
Forum discussion continued at WebmasterWorld.


Comments:
rich
07/21/2010 01:25 pm
I also just saw my first matching results today!
Shawn M
07/22/2010 12:21 am
I am starting to see more and more matching now that MSN and Yahoo are combining their results
lemiffe
07/22/2010 06:57 pm
Couldn't give a toss about Bing nor Yahoo, both obsolete in search technology.
Tom Nolan
07/23/2010 08:02 am
I'm interested to see whether when Bing & Yahoo are fully intergrated and all the publicity that will go with it...will it actually have any effect on Googles market share...unfortunetly i suspect not!
Mike
08/03/2010 06:46 pm
I have started seeing the same thing. I have gotten more traffic than normal due to the times they are testing.