24. Learn about accessibility law in your country.
I live in the U.S.A., and therefore, while WCAG 2.0 is the guidelines I aim for, we usually refer to "Section 508" or features being "508 Compliant" because that is a section of the Rehabilitation Act of 1973. Actually, there are two areas in the Rehabilitation Act that relate to disabilities. The first is Section 504, which declares that the act "prohibits federal agencies, programs, or activities from discriminating and requires reasonable accommodation for qualified individuals with disabilities." Section 508 declares that "agencies must give disabled employees and members of the public access to information that is comparable to access available to others." A basic checklist of Section 508 compliance can be seen by clicking on the link.
Notice anything interesting there? Did you see anything mandating that Accessibility is the law everywhere? Nope. Just in the services and the fund allocated for them by the federal government. Is there a strict standard? Again, nope, but Section 508 by virtue of being a policy of the federal government, and with the sheer volume of software seats that the federal government provides, can carry a lot of weight in regard to the design decisions of companies.
I know for a fact that a large agency of the federal government looking to purchase a lot of software from my company was what initiated a thorough review of Accessibility requirements and areas that needed to be updated in our product so that they would buy it. The dollar amount of that deal most certainly played a part in why we undertook a large-scale retrofit of our product to meet Accessibility standards, and again, the standard we measured for that purpose were the guidelines as described to meet U.S. requirements. To meet the broader WCAG 2.0 requirements means we still have a distance to travel still.
For a nice breakdown of what USA Laws do and don't cover, see http://webaim.org/articles/laws/usa/