Before you disable comments take note of this:
I clicked on the link that Dan left and read Seth Godin's blog. I wondered why I had never subscribed to his feed before. The reason -- Seth Godin doesn't have a feed.
I wondered why. Looking at his blog site, I see that his monetization comes through selling his books. Those ads wouldn't appear in a feedreader and since he doesn't allow comments, subscribers would never have a reason to access his site if they could just add his blog to their feeds.
So, if you have monetized your blogs with something other than an ad network such as adwords (which you can add to a feedburner feed), it would be counter productive to disable commenting.