A related El Reg story - court rules there was discrimination: http://www.theregister.co.uk/2007/01/25/computer_based_exam_discriminated_against_blind_candidate/
Internationally the first celebrated case was the Sydney Olympics website, whose operators had to pay up for gratuitously excluding a blind reader.
The web is accessible by design. In general it takes a lot more work to break that design and make a site inaccessible than to get it right, though there are a few cases where the laziest approach is not the best (alt being the most obvious).
There are tools to help web developers evaluate accessibility (I've written some of them, as well as served with W3C as Invited Expert on the subject). What's lacking is any kind of budget for them: I had to abandon that work when the money ran out, so my tools are looking a bit dated in the era of HTML5.