Oh, okay, so Google changed (like a year ago now) the way no-follow works.
It used to be that if you had four external links on a page and one had nofollow, each of the remaining follow-able links got 33% of the 'link juice' from your site, theoretically increasing their page rank.
Now if there are four external links and one has a nofollow, each remaining link gets 25% of the juice, theoretically LOWERING their page rank. This was done to prevent link-sculpting.
And ... eh. It only matters to the sites you're linking to, it won't lower your site's page rank. I don't think it's a big enough deal, IMO, and besides, it's not the PLUGIN that's putting in nofollow on your links, it's Twitter :)