In his article Using REST with Ajax, Nic Ferrier highlights an interesting property of the XmlHttpRequest object used in browser side JavaScript. The object can use all of the HTTP verbs, which is impossible to do from straight HTML. So in some sense Ajax makes REST implementations of Web services easier and vice versa. If you need to use PUT and DELETE as part of your REST protocol, then a client side UI can take advantage of all the standard idioms.
Learn something new every day.