The ADA has been criticized on the grounds that it decreases the employment rate for people with disabilities and raises the cost of doing business for employers, in large part due to the additional legal risks, which employers avoid by quietly avoiding hiring people with disabilities. Some researchers believe that the law has been ineffectual. Between 1991 (after the enactment of the ADA) and 1995, the employment rate of men with disabilities dropped by 7.8% regardless of age, educational level, or type of disability, with the most affected being young, less-educated and mentally disabled men. Despite the many criticisms, a causal link between the ADA and declining disabled employment over much of the 1990s has not been definitively identified.
For most businesses, the need for ADA web compliance means they will need to make at least some adjustments to all of their online marketing strategies. For instance, if your company provides tax preparation services, all of the tax forms you provide for customers to download would need to meet accessibility standards. Any online tax preparation services that you offer would also need to be configured so they meet ADA standards, as would your mobile app.
This past September marked the first time a judge ruled that the ADA applies even to businesses without a physical location. Scribd, an e-book subscription service is considered to provide "a place of public accommodation." Their services are not accessible to blind persons because they cannot be read with a screen reader. The judge reasoned, "Now that the Internet plays such a critical role in the personal and professional lives of Americans, excluding disabled persons from access to covered entities that use it as their principal means of reaching the public would defeat the purpose of this important civil rights legislation."
Just as you wouldn’t trust an overweight personal trainer or a skinny chef, you should probably never trust a designer with an ugly looking website or an SEO specialist who doesn’t rank well on Google or an “internet marketer” who uses direct outreach to generate leads. And by that I mean, if someone is selling you the idea of getting traffic through Google or Pay Per Click or Social Media, but they’re using cold outreach, like, they’re direct emailing you or they’re using word of mouth to get in contact with you, they’re really not practicing what they preach.
UPDATE: Since writing this post in August 2017, several important changes have taken place in the laws regarding ADA compliance for websites. On December 26, 2017, the Department of Justice announced that they have withdrawn the Obama-era Advance Notice of Proposed Rulemaking mentioned in this article which intended to require ADA website compliance. The DOJ’s withdrawal announcement stated, “The Department will continue to assess whether specific technical standards are necessary and appropriate to assist covered entities with complying with the ADA.”
While legal considerations might be your biggest worry, making your site more accessible is simply good customer service. More than 39 million Americans are blind and another 246 million have "low vision," Another one million are deaf in the U.S. Add to that people with mobility issues that prevent them from using their hands and that's a huge portion of the country's buying power.