I'm not yet running a professional website, but I've run an academic website for about 3 years now. Despite iterative attempts at prominent contact information for everything from research collaboration to code questions, I've only had one person contact me. This despite getting close to an average of 80 hits a day.
HN, what do you do to encourage communication?
(in case you want to see the site in question: http://sites.google.com/site/thomasroderick -- its still a little under construction)