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Here's what I would do if I were Google: has the site proven to be a quality site without a doubt? Then nofollow links has some worth. Is the site somewhat dubious and spammy? Then discount all nofollow links.
In a recent video on nofollow links, Matt Cutts appeared to be taking the "other way" out, basically saying that, "If wikipedia decided to remove the nofollow tag from some of the outbound links that it trusts, we would support that."
For example, in Google's algorithm a dofollow link from an obscure free directory supposedly counts for more than a nofollow link from the New York Times of Harvard University.