There are two ways to persuade someone - you either use pain (the stick) or pleasure (the carrot).
Legal requirements are usually presented as a big stick to force organizations to comply, but it hasn't been an effective stick. Very lax enforcement and no negative examples available of what happens when an entity doesn't care about making online presentations accessible.
But, that may be changing. eCommerce quickly moved away from using Flash or other plugin dependent content when user's voted with their credit cards but it's only recently that they've been forced to consider the deeper impacts of inaccessible site design. The Target lawsuit, studies showing negative online perceptions impacting the bottom line, the dismal ratings given by the U.N. are highlighting the problem on eCommerce sites, can eLearning be far behind?
What are the other sticks and carrots availble to persuade decision makers that a focus on usability is worthwhile?
A site with some great faculty development resources is the DoIt centre at the University of Washington http://www.washington.edu/doit/
Check out their videos. If you are at the U of S I have a stack of Working Together: Faculty and Students with Disabilities videos that I would give away.
NY Times, 1-1-2001, Web Access for Commerical Sites
RELATED WEB SITE OF INTEREST
"Selfish Reasons for Accessible Web Authoring."
"...a list of purely greedy, self-serving, un-altruistic motives for making your page widely accessible."
Certainly for commercial sites, they can't then use the arguement of "what would a disabled person want with my super-fast skateboards" or whatever they are trying to see.
For any presentation, simplier is better. I recommend always starting with the simpliest and then adding complexity only where it's needed because each layer of complexity requires more elements, increased costs, to keep it accessible. Text > Images > PDFs > Audio > Flash/Video. The simpler your presentation, the less it costs to develop and maintain, while making it easier to increase your user's ability to access the content.