I'm posting on behalf of Rand who is currently busy at SES Chicago. 

Prior to today if you wanted a link from SEOmoz all you had to do was sign up for an account, edit the URL field in your profile, and add a blog comment.  We left this in place simply because we didn't care if the strength of our outbound links was diluted.  Although SEO was high on our list of considerations when creating this site, it certainly wasn't the driving factor.  We were more focused on delivering a killer site with great content.  Rand informs me, however, that we've been suffering in the search engines due to a high number of outbound links to bad neighborhoods.  So as of a few minutes ago all the links on your profile pages have been nofollowed.

Good news, however!  The new SEOmoz is very close to being finished and we've got a system in place that will allow our active members to keep their profile links without a nofollow attribute.  I won't go into too much detail right now, but if you regularly write comments on our site and are involved in our community your profile will allow you to have a link without a nofollow.  This mechanism should effectively filter out spam and keep all the regulars happy.