Accessibility is important. Not only because it is a legal requirement in several countries, but because those laws were introduced because access to information is a real issue for the millions of people that have a disability that limit their access to information.
It's easy to assume that this is something that applies only to large corporate sites, or government services, but with blogging taking on more and more of a role as a social and political soapbox, lack of accessibility has the potential for causing significant exclusion.
This is particularly unnerving considering how easy it is to make a website accessible - generally all it takes it a little knowledge, and putting a little bit of thought into it whenever you add content or modify your templates.
So make your site accessible. I've not yet cleaned up my blog - I only installed MT a couple of days ago, but I've made a few initial steps, thanks to Dive Into Accessibility - a great introduction to accessibility techniques which also provides a detailed rationale for all the suggestions provided, and to
Bobby WorldWide, an automated accessibility testing tool.