I was directly involved with OS projects for over a decade. At one point, a major OS CMS project invited me on board *specifically* to make the system accessible (both front and back end). After a year of code re-writing, providing proof of concepts, fixes, suggestions, education, etc, the vast majority of suggestions went ignored. The team said "if people want accessibility, they can build a 3rd part add-on".
I also provided feedback on a lot of other projects. Talking to core team folks at tech conferences, interacting on forums, emails, etc. Even giving bits of code to change. No great success there either. Some bug fixes that were lodged as far back as 2008 were never implemented (not the suggested solution, nor another solution to the problem).
But after giving so much of myself to FOSS, and getting nearly no buy-in from developers and site owners, I'm with Adrian – I am not giving it away for free anymore. Well, that's not quite right: I still help people who ask me and who have shown that I won't be wasting my time.
I gave a talk to Confoo in Montreal a few years ago that covered some of these issues = "Accessibility: No Rights without Responsibilies" http://incl.ca/accessibility-no-rights-without-responsibilities/
Now, I'll write a blog post, or write a tweet, bring it to the attention of the people in charge, and that's the end of it.
And it does work. @eonetimepieces makes wrist watches that can be used both by sighted and blind users. Their current website is a horror of parralax design that is unusable. A couple tweets at them and they inform me they are redesigning the site from the ground up, involving accessibility folks in the process. So now, I wait and see what they come up with.