I guess on a normal basis our comments can get between 5-20 a post, depends on how frequently i've been posting too. I'd like to be ambitious and get in the 50-100 range, but I have "depressing content syndrome". I do my best to mix it up with the humor of life in general, but people know what they're getting into when they get any kind of emotional involvement with us.
I'd love to average around 50-60 comments per post.
Check out http://metrodad.typepad.com. He gets a ton of comments for each post. One received 294 the last time I checked...now that's some active readership! I keep wondering if he has a huge family/friend base or if it's actually strangers (like me) reading his blog and posting comments.