Jeremy Zawodny posts his commentary on the NoFollow tag after finding an interesting blog entry on how the NoFollow attribute has changed linking behavior. NoFollow was introduced by Google over a year ago to combat prevalent comment spam as blogs became extremely popular. Ever since, NoFollow has had mixed responses from Webmasters, and Jeremy nicely puts it all in perspective.
NoFollow has done very little to actually thwart comment spam, and its other effect is to dissuade some from entering legitimate comments. Without a reciprocal link, what motivates readers from commenting on someone else's website? Jeremy notes the "psychology of linking" has changed, and people now ration their linking. It should really be up to the search engines to sort out linking and its prominence in the algorithm for ranking sites.
Jeremy's advice is try not to over-think the issue; link and be linked to! Life's too short.