WCAG 1.0 has been published back in 1999 by the Web Accessibility Initiative (WAI) of the World Wide Web Consortium (W3C). Since that time both the Internet and all the technologies have evolved. The Internet itself has got way different character: together with the commercial side, the social networking has evolved. The only thing that hasn't change so far are the accessibility requirements still remembering the good old HTML 3.2.
While WAI keeps working on WCAG 2.0, the WCAG Samurai (a group of web developers and accessibility experts led by Joe Clarks) has posted an Errata for WCAG 1.0: a set of changes which reflect the evolution of the Internet and various media. The most important I have found myself was saying 'No' to the Priority 3 of WCAG 1.0: it seems like the group responsible for defining the accessibility standards has understood the feedback they got through the time.
Until WCAG 2.0 is done, the WCAG Samurai errata gives web developers and web designers a new point of view of accessibility of the modern Internet what will hopefully lead to more accessible web sites.