I believe that accessibility is important overall on the web for a number of reasons. First because of people who are visually challenged. Their screen readers can work when the text is there. However, the more important reason is because of alternate browsers like PDAs and phones. If you have a site that can be seen in a secondary text-only mode, more people can see your site.
Our site hawkridge.org should have accessiblity, but it is not priority number one. If people are visually challenged, more than likely, they won't be going to go bird watching.