Rather than recapping what's already been said elsewhere, here are a few different (and interesting) articles that can add insight to the discussion:

http://www.verticalmeasures.com/link...-vs-do-follow/
http://www.sitesketch101.com/nofollow-vs-dofollow/
http://tech-seeker.com/blog/dofollow...be-using-them/

Ultimately, a platform like WordPress - particularly using something like HeadSpace gives you a lot of control over how search engines interact with your site.

The more you can CONTRIBUTE to other high-ranking blogs that allow DOFOLLOW, the more you can increase the value of your own site. Using a mix of DOFOLLOW and NOFOLLOW on your own outbound linking *from* your site tells search engines that you are working to moderate your content a bit which seems to also have a value.