The blog we have here is integrated with the forum meaning that guests can't post comments. Only members can post so it only generates comments from users which are 99% of the time useful.
I get a fair amount of decent comments on the hortorian blog. On my personal one, Earldust.com, it's basically a load of spam w/ a few decent ones. I'm not to concerned though.
I have a blog on myspace that I have been writting in for years. A few of my friends comment on my postings there. But I have to accept their friend request for them to even be able to read that blog.
I just started a wordpress blog like litterally yesterday and Ive had a couple comments just from Princess and Jughead, no spam yet..
I heard if you make your comment links DoFollow on Blogs more people are willing to comment since comment links are no-follow by default in Wordpress, and many other blog software.