One of the reasons websites aren't accessible to the blind is because the client prefers style over function. As already mentioned, Flash content instead of HTML, or even simple things like copy writing (for example, link readers require a hyperlink to be a description of the thing the link goes to, for example "click here to download our brochure" as the whole link rather than just the "click here" part. A website full of "click here"s tells a link reader user nothing at all but a trendy client might want it that way for style).
And for many, many sites, I think it's absolutely fine. For example, some of my clients are publishers. They might want a microsite for a niche market book - if there are no plans for the book to be released in audio then it's safe to say the client's target market is not the blind, and that the client doesn't need or want to spend extra money making the site accessible on the offchance that one of the visitors can't see. I have no issue with that. It's not cost effective or necessary for EVERY site to cater to the blind because the chances of a blind person visiting that site are pretty slim. So if my clients say "I want a Flash-only site", then it's fine. I always, always point out accesibility issues at the start of every project (not just for the blind, but for people in, say, poorer countries who are less likely to have the fastest machines and the latest browsers). Then the client makes a judgement call based on their priorities and budget.
However, for an e-commerce site, especially one for a huge retailer, there is simply no excuse. Ditto for government sites, public information sites, charities etc. Where the target audience is 'everyone', then that is by definition going to include some blind people.
It's not one of these subjective things you know. You can figure out fairly easily if they broke the law.
That's nonsense. Every day, precedents are set in court and the law is interpreted and examined precisely because it is not necessarily clear that someone broke it. Sometimes it's not even clear what the law
is. The law doesn't say "websites have to be accessible to the blind" or "websites must be developed to W3C standards". The law says something along the lines of "retailers must take reasonable steps to ensure their facilities are available to the disabled" or some such. How that is interpreted and implemented is down to lawyers and judges.