Moderate use of nofollow

Google introduced nofollow a while ago; it was initially designed to be used in blog, but it's more widely used now.  You certainly don't want to let spammers do whatever they want to do, but link is what makes web, so ... I don't think it's a good idea to use nofollow everywhere.  What's your take?  I am using nofollow in blog comments, but I am not using this in my forums.  Do you think that nofollow should be used in moderation?  If so, how do you define moderate use of nofollow?