Accessibility & Drupal: Who's fault is it?

Who's to blame for the accessibility of a Drupal site? Who's responsible for the accessibility of a Drupal module?

Accessibility in Drupal is often forgotten, or confused with being taken care of with user experience.

Web content is increasingly produced by our clients, the end user, without extensive web design skills nor knowledge about accessibility. The primary question is, How well does Drupal support the creation of accessible web content to all authors, irregardless of experience or ability?

The quality of Drupal in supporting accessible content creation is critical. It's more than marking off a checklist. It's about making that accessibility sustainable through the life cycle of that product.