Really what you are dealing with is “Free-speech” and it is a doubled edged sword to the blogger.  By allowing comments you allow interaction with readers and by allowing trackbacks you allow interaction with other blogs.  While this is all well and good, this interaction can often be a nuissance to big sites, but will rarely keep you tied up with a site that is growing.

Not only do I recommend that you allow comments, I suggest that you allow users to link back to their website.  Now I know that some are scratching their heads, saying “why would I allow a competitor to put a link on my site?”  Believe it or not, this will benefit you in the long run.  First, those blog owners who are in your niche and just starting out need links and they know it.  Because of that they are usually motivated to leave thoughtful relevant comments in hopes that the blog owner will allow it.  Getting a discussion going in comments is a good thing, and a good way to get someone to bookmark your site.  Sometimes they are not even interested in your site, but they are interested in seeing responses to their comments.  If you don’t allow users to link back to their site, you are repelling good comments.

If you are attracting blog owners who are leaving legitamate comments, then visit their site and do the same.

ADVANCED STRATEGY:

If  you know PHP or a scripting language, then you can automate this process.  Run a CRON job, that goes through your comments everyday saving urls from comments.  If the page is a blog, go to most recent post page and leave a comment saying:

“I enjoyed this post, great blog you have here.  Thanks for the visit to my site!”

or something stupid that has a good chance of getting through moderation.