I just disabled comments for anyone that comes here via Google. I get random comments every few days from people who discover ooooold posts leave comments on them. I don't have any problem with seeing the comments because of my comments feed, but it's sort of a waste of their time and mine. Just now a comment was left urging me not to move to Philadelphia was the last straw. I mean, how many months ago did I quit that job and announce I was going to San Francisco? And a few days ago someone was urging me to give Struts a try (after I had bitched a bit about it) when all I'm doing right now is heads-down Struts stuff.
Most Googlers don't know what a weblog is or realize that the posts are well past now, so to avoid those quick insta-comments from helpful searchers, I've just disabled the comments if your referrer says you've arrived here from Google or Yahoo. Very simple solution. If they click around and get an idea what the site is, the comments return (as if by magic).
I think that should help.