An excellent post here by Dave Thomas on PragDave, one of OG Pragmatic Programmers.

He really drives home the point of server-side applications needing to be client-independent, not assuming the client is a browser, and spitting out just HTML.

Favorite antagonistic quote:

Recently, folks have been trying to circumvent this simplicity by making browser-based applications more interactive using technologies such as Ajax. To my mind, this is just a stop-gap until we throw the browser away altogether—Ajax is just lipstick on a pig