Do you use Dofollow or Nofollow for comments in your blogs

[scheng1]

I notice that many experienced bloggers, such as Probloggers, are allowing Dofollow in their comments.
some of the blog posts have closer to 200 comments, the most I have seen is 400+ comments. They use nofollow tag for affiliate link and banner link. Since their blogs are PR4 to PR6, the dofollow feature allows us to create valuable backlinks to our blogs.
Most of my blog posts are also dofollow, except for some of the earlier ones when I listened to wrong advice, and put nofollow.
Do you allow dofollow or nofollow for comments in your blogs?

[automobileplanet]

This do follow and no follow are strange words to me, kindly explain.

[bloghub]

This do follow and no follow are strange words to me, kindly explain.

using 'nofollow' in your url tag, google will still crawl the external sites but will not take into account of pagerank..

Hope it helps.

[Green Iowa Energy]

There is alot of debate about dofollow and nofollow. I've tried both on past blogs. Only difference I've noticed to date is when people start to notice your comment section is dofollow, you end up battling alot of spam comments. Its like your website gets put on a list for spammers or something.

I would like to truely know how dofollow and nofollow affects your pr.