We have a large authority site that just disappeared. All of the results now just show the title, no description below in the serps, and thousands of pages don't appear. Keep in mind, that this is just a simple content page, nothing fancy, and certainly nothing strange or black hat in any way... I like Yahoo and I've been rooting for them for some time. In my particular industy, the serps are full of lots of spam...lots and lots of spam blogs and sites that really don't have any good content.