whoisgregg - 12:13 am on Sep 25, 2012 (gmt 0)
To be honest I don't see how your developer saw it made sense to have the page loaded and then a further AJAX/JS request having to be made. It kind of defeats the advantages of AJAX and obviously the content not being immediately visible is a drawback.
By the way, this is how all of Facebook functions. ;)
The advantage of a purely AJAX driven site is that all subsequent clicks don't have to reload the header, footer, navigation, etc. -- just replace the main content area. This can massively impact the perceived load time of the entire site.
This can be accomplished by modifying the browser URL state (either with pushState/onPopState, which is only supported on bleeding edge browsers) or with hash-style URLs. Google has a document for one way to implement this that they will support:
Making AJAX Applications Crawlable [developers.google.com]
Oh and if I had a developer make a site that way for me without clearly explaining they were going to implement a very unusual method, I would also be Not Happy.