[smackfu]

Yes, that's a real issue. I've had to add JAWS Screen Reader support to an app, and even after you shell out for the thousand dollar license, it's very difficult for a casual user to use it in the same way that an actual blind user does. Ideally you test with an actual impaired user, but they have real jobs and don't want to spend all their time testing your apps.

[DanBC]

There's a gap in the market for usability testing. This would mean that things are not just validated against specs but checked in real world use.

There are probably many groups already doing this stuff. Perhaps they just need better organisation or SEO?