REST The rest of the message doesn't read like that. I'll pretend you wrote "HTTP API" instead.
Any other thoughts on such an application design? In addition to what Brian said, Google built a convention around hash fragments to make AJAXy resources crawlable. It's a hack to accomodate people who didn't know better about the drawbacks and are now stuck with their horrible design. I call it a hack because AJAX by itself, unlike other Web tech we have seen so far, does not degrade gracefully; see and puke for yourself: <http://code.google.com/web/ajaxcrawling/>
Since you are still in the design phase, design your interaction properly with *progressive enhancement*. Write semantic markup and forms that work in a text browser. Then apply styles. Then apply JS that modifies the behaviour of an existing document to load partial content with AJAX. Employ pushState so that the URL changes the same way like it would for a user agent without JS. I can recommend jQuery BBQ to handle these bits.