Yahoo's algorithim is really really bad. But they have only been live with that search for a week or two.
They have more IP based url's indexed than domain ones. And they do a piss poor job of determining duplicate pages. So they end up indexing both the IP address and the domain.
They also put way too much weight on the page titles in the algos.
But I'm rooting for them, I hope they improve enough to take more of Google's market share.