Yahoo! signs Twitter real-time search deal, but why?

So Yahoo signed a deal with Twitter to provide real-time search functionality. Which is actually interesting, because Yahoo already has a deal with Microsoft to use Bing as a search provider, and Bing already has a deal with Twitter for real-time search.

So this begs the question: Why? It seems like Yahoo basically gained nothing but PR from this deal. The only possible reason I can think of is that the search volume is so great, that Twitter limits the number of API queries and so Yahoo need a separate agreement. But that's almost as dumb as the PR reason.

The Telegraph article says:

"... what is different to the Google and Microsoft deals with the microblogging service, is that Yahoo! has effectively made itself a Twitter client, as Yahoo! users will be able to tweet from multiple locations across Yahoo!'s products. It is unknown how this will be carried out at this stage. There is a possibility it could happen via widgets."

Personally, it sounds kind of far-fetched to me. I mean, sure, it could happen -- but why sign so early if that's what you're trying to do? It sounds mainly like a PR move meant to keep up with the other search engines.

Tags: bing, microsoft, search, twitter, yahoo