There were whispers at the recent search engine strategies conference on possible penalities Inktomi has been issuing in the past few months. Yes, there have been outbreaks too. One in particular was the penalization of sites that contained footer navigation with a certain amount of cross-linking going on between sites and also internally. Now, while footer navigation is a good method for search engines, Inktomi seems persistant on the "pages need to be designed for the users, not the engines" ideology. What interests me, is if this particular penalty is a manual editorial review or incorporated into the algo as a temporary ranking penalty. If you have been penalized by Inktomi, this might be worth checking out. Several members of SEOchat have also posted other penalities that have arisen recently, and their thoughts about this possible reasons.
Check out Inktomi Penalizing Footer Navigation here.