I say graceful degradation, you say progressive enhancement

I have written about graceful degradation for Ajax apps before, some of it in the context of the unsafe GET fiasco in the Ruby on Rails world.

Jeremy Keith calls the concept Hijax, which is the topic of the talk he gave at XTech 2006.

I intend to write more about the topic sometime soon(ish?), but in the meantime, you can look at the slides for the talk for an introduction into the idea.