How exactly does nofollow affect SEO? For example, A links to B and B links back to A but uses a nofollow tag. Obviously A's link to B passes PR and B's link to A does not, but what about the details? If B's link to A uses the keyword "Widget" for anchor text, does A rank any higher for the search term "Widget"? In other words, does a nofollow link still affect rankings without affecting PR?
What would be a use of 'nofollow' if this could affect ranking? Could it prevent a spam? Just no... it makes no sense.
Given that nofollow was created by Google to combat blog comment spam, I would suppose that all benefits are removed from a nofollowed link, not just passing of PR.
its similar to trackback marketing with blogs, you link to them and they get spidered - its as simple as that
nofollow links show up in backlinks. I guess it's not totally correct to say that they're absolutely no good even for Google.
It could still help you in the Serp because if relevant to your niche, it builds traffic. It does not help at all with PR. It is still a good way to advertise if you target the audience that would be interested in your niche.
Building traffic won't help you in the SERPs. But then if your traffic is high enough from these links, you won't need the SERPs.