As I am one to jump on the bandwagon, a movement has started to re-allow the following/spidering of comments on blogs from search engines. The original idea was to discourage content spammers from increasing themselves up the rankings. As I’m on top of the spam on this site, I don’t think its fair on genuine human comments not to be “followed up” on by the spiders.
I’ve installed a new plugin called DoFollow which gets rid of the nofollow tag on links within post comments. Randa Clay has also come up with some basic logos to use so that your readers can be informed that their links will be a little more valuable.