Do you notice? If your pages are cached nearly same days on Yahoo and Bing then our keywords are at same position on both search engines.
Cache report I haven't noticed but keyword rankings, yes, they look similar on both. And I feel they both need to come-up with things that can actually increase their search users!
as far as I know, it is because search results of Yahoo are now powered by Bing..that is why often times you can get the same result from two search engine..