To give you a quick briefing in case you don't know what nofollow is, it basically makes Google and perhaps other search engines ignore links. What does that mean? Less people will find your site. Most of us want people to find our sites, that's why we have them! There is a good reason the nofollow attribute to links was created though.
"Preventing Comment Spam" That's what Google says they're trying to do with the - rel="nofollow" - tags for HTML links. They even give an example of what they're talking about referring to links with text of "discount pharmaceuticals."
I will be having each individual comment screened/moderated to make sure there is no spam, so you don't have to put up with it, and so it doesn't get any of Google's attention. By moderating those comments, I think I have rendered the reason "invalid" for sustaining a nofollow attribute to links.
More people who don't use nofollow:
There are others who find reasons to not use the nofollow as well:
Wikipedia Steals Link juice
13 Reasons Nofollow Tags Suck
Good riddance nofollow
There are good reasons for nofollow tags though, they really can help battle spam and paid link problems, but the paid link problem doesn't really go away, it just makes it so those who keep better secrets about paid links more profit.
If you want to get rid of nofollow tags though, fear not, you can!
If you use Blogger (Beta), a tutorial on removing nofollow for your heavily moderated comments can be found here:
Remove nofollow attribute on comments
If you use Wordpress your tutorial can be found here:
Nofollow << Wordpress Codex
For other platforms and the ones mentioned, there is an "Ultimate list" of dofollow and nofollow plugins as well.
Tips: If you don't use nofollow, moderate your comments not with an iron fist, but with the chainsaw from the movie Army Of Darkness, one that never runs out of gas. Do that simply because it would be too uncool to do otherwise.