I found this article saying yahoo does follow "nofollow" links although does not give weight to the link:
1. How does your search engine treat the No Follow attribute?
- Google (Adam Lasnik): The Googlebot does not follow that link.
- Yahoo (Tim Mayer): If we find a link we make it available to our algorithms to find new content, whether it has a ?no follow? attribute or not. However, if the ?no follow? attribute is present, it means that no attribution is given to the target from the source of the link.
- Ask.com (Ask Search Team): We have never officially supported No Follow, so your questions don?t apply to our crawler/ranking.
http://www.searchenginejournal.com/h...ttribute/4801/