The gray area is a matter of scale and purpose. If you have a small business which serves as specific market it's a good idea to make the site as user and disability friendly as possible. If, however, your market serves segments with a likeliness to have various handicaps or disabilities you should address that with an ADA Compliance review of the site. Also consider the scale and purpose of an organization. Publicly traded large businesses need to concern themselves more than a single location family owned retailer and if someone sues your flower shop because the text was too small or didn't have "image alt tags" causing them distress... That's pretty frivolous and would likely not stand.
This is the reason why I think web design firms have to position themselves as solution providers and not just web guys/gals. A client doesn't need a website, they need sales. The website is just part of that solution but it's not the solution and unlike web design, service like email marketing automation, SEO, and PPC requires an experienced professional.
Error prevention on important forms (3.3.4): For pages that create legal commitments or financial transactions or any other important data submissions, one of the following is true: 1) submissions are reversible, 2) the user has an opportunity to correct errors, and 3) confirmation is available that allows an opportunity to review and correct before submission.
For Avanti Hotel to address the issue and make its website ADA compliant, it will cost around $3,000. However, oftentimes businesses must pay damages to the plaintiff on top of making the fix. In this particular case, the settlement is expected to be between $8,000-13,000. If the owner chooses to fight, damages plus lawyer fees could put him at more than $25,000. This is a heavy burden for a small business.
The ADA is the Americans with Disabilities Act, passed almost 30 years ago in 1990. This act was originally put in motion pertaining solely to physical location. It requires establishments to provide people with disabilities easy access to various levels throughout the business. This act was set to achieve an equal experience to all people, handicapped or not.