Yahoo! has issued an other index update this past friday. The updates are occurring more frequently these past several months, in order to make "improvements to the indexing system," according to Yahoo. What I have seen is an incredibly large drop in SEM community buzz on Yahoo! Search. So much so that the major forums with Yahoo! Search sections have been fairly inactive for days on days. This does not include the Yahoo! Search Marketing division, that runs the paid side of Yahoo! Search.
Forum discussion on the update at: