No-follow/do-follow

I'm curious what other people think of the "do follow" movement.

(Short explanation: wordpress (and other blogging platforms, I suppose) adds a "no-follow" tag in the link you leave in your profile when you comment on someone else site. Search engines won't follow you. Therefore, you don't get "credit" for the link. It's supposed to dissuade spammers.)

Anyway , I've seen a couple of blog posts in the past few days for the "do-follow" plug-ins, allowing commenters the link back to their sites. I'm not totally sold on it. I think it could encourage useless commenting only for the link.