Matt May (W3C WCAG dude - if dude and those acronyms have a place in the same sentence*) makes the point that, first of all, asynchronous server interaction is not new (it’s just a new, improved flavour) and secondly if those people who are pushing AJAX as the ‘new great thing’ don’t think things through thoroughly, there’s going to be trouble:
There are other discussions about the topic, such as this one over at Standards Schmandards which I would strongly advise the standardistas who are thinking of using AJAX to read before untold damage is done. I would not recommend this page, however.
Ajax - the new DHTML? You decide …
* [I jest of course - I know Matt, and he's no freaky, bearded, big jumper-wearing brainbox with poor social skills and bad teeth. That was someone else I met at SXSW ...]