If you ask me, the positives of blog commenting overpower the pain involved in moderation. The comments sometimes (unknowingly) let you target some really profitable keywords...
To combat spam, you may:
- Nofollow blog comments
- Deny access to spammer IPs
- Verify that the visitor accessing the site is a human
To dig deeper, check this:
http://blog.pagespot.org/page/item/5...d-website.html