Hey Casey, this is one of the areas where things get a little weird because the W3 doesn’t actually have any say over the ADA guidelines, it is more than the ADA guidelines adopted the WCAG 2.0 guidelines as just that, a guideline to help. As far as I know, the tool you’ve linked to hasn’t been used in any judgements I’m aware of. Usually when it comes down to making a decision on if something is/isn’t compliant they have people use the actual PAWS tools and show what elements do/don’t work as intended or are otherwise inaccessible. Hope this helps!
Courts have essentially taken three positions when approached with this issue. Some courts take the position that the ADA applies to all commercial sites because the law was meant to protect disabled individuals from having a more difficult time than able-bodied individuals from doing business. That is why the website Scribd was unable to get a case summarily dismissed and ended up settling.

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.

That carousel or image slider on your site looks beautiful. That stunning video on autoplay may have cost thousands to produce. Users with cognitive limitations, however, may not comprehend your information quickly enough before the view changes or your video ends. Other users may want to start over, or go back and review something they saw or heard.

While new companies might not prioritize web accessibility simply because of price, it can be seen as a great insurance policy. Even if you don’t fall into one of the categories mentioned above, if you want to prepare for the future and ensure no lawsuits, becoming web accessible is the way to go. Not to mention being available to persons with disabilities is very important and says that you care.

Thanks for writing. While I’m not a lawyer I believe if your physical practice is ADA exempt your web presence, as an extension of that physical business would maintain the same exemption status. If you’d like to be absolutely certain I’d confer with an ADA lawyer (email us, questions at yokoco dot com if you need a referral) but I don’t believe you have reason to worry.
Poorly designed websites can create unnecessary barriers for people with disabilities, just as poorly designed buildings prevent some people with disabilities from entering. Access problems often occur because website designers mistakenly assume that everyone sees and accesses a webpage in the same way. This mistaken assumption can frustrate assistive technologies and their users. Accessible website design recognizes these differences and does not require people to see, hear, or use a standard mouse in order to access the information and services provided.
Many people with disabilities use assistive technology that enables them to use computers. Some assistive technology involves separate computer programs or devices, such as screen readers, text enlargement software, and computer programs that enable people to control the computer with their voice. Other assistive technology is built into computer operating systems. For example, basic accessibility features in computer operating systems enable some people with low vision to see computer displays by simply adjusting color schemes, contrast settings, and font sizes. Operating systems enable people with limited manual dexterity to move the mouse pointer using key strokes instead of a standard mouse. Many other types of assistive technology are available, and more are still being developed.
As organizations around the world scramble to bring their sites into compliance with the World Wide Web Consortium’s Web Content Accessibility Guidelines (WCAG), focus on other, preexisting accessibility regulations has also intensified. The United States’ Americans with Disabilities Act (ADA) is one of the most visible and complicated pieces of accessibility legislation. Let’s look at some of the ins and outs of what an ADA compliant website means today. Or, if you're interested in seeing the nitty-gritty details of your site's accessibility, request a free website audit report using the form on this page.
If posted on an accessible website, tax forms need to be available to people with disabilities in an accessible format on the same terms that they are available to other members of the public – 24 hours a day, seven days a week, without cost, inconvenience, or delay. A staffed telephone line that sent copies of tax forms to callers through the mail would not provide equal access to people with disabilities because of the delay involved in mailing the forms.

The words in the tag should be more than a description. They should provide a text equivalent of the image. In other words, the tag should include the same meaningful information that other users obtain by looking at the image. In the example of the mayor’s picture, adding an “alt” tag with the words “Photograph of Mayor Jane Smith” provides a meaningful description.