I follow comment and blog links. NoFollow is the equivalent of a high fence around the yard. The power of the blogosphere is in its decentralized and organic form. There is a lot of noise out there: legitimate blogs that have nothing worth saying much less reading, spam blogs which clog servers and no one reads purposely, and spam comments which profit on others hard work. But the good blogs rise to the top usually, the ones with value and appeal and real content (the veracity of the content is entirely secondary).
NoFollow settings in blogs are simple tags that prevent links back to a blog from a comment. These NoFollow tags were a basic from of spam prevention, removing the benefit of the comment spam (links back to the spam blog). However, there are tools out there (such as Akismet, which I run on iPandora.net) which filter based on content without the need to block links.
When I want others to read my blog I must first allow them to find it. Instead of buying advertising and annoying people until some random dupe is duped into reading my blog, I’d rather give to receive. By reading and commenting legitimately on others blogs I do the equivalent of saying “hello” to my neighbor. The neighbor knows I exist and that I at least appear to be humaniform. If my comment is good, other readers will follow the link in the comment back to my site. A NoFollow tag does not allow the links back to the commentors site, isolating the blogs from each other and preventing a follow-through reader finding another (hopefully worthwhile) blog.
Being a bottom-rung blogger (about 50 people per week read iPandora.net) I benefit greatly from each and every person who reads my blog, and even more from those who comment (hint hint). Using a blanket approach to any problem is harmful to people like me more than to the larger, A list, bloggers. They have no moral obligation to allow the links, but it’s nice when they do.