If your assertion is that developers can write bad code, abuse HTTP semantics, defeat caches, break navigation etc then so what? With the ability to do things right comes the ability to mess them up.
I am saying that by using Ajax to partially update a page, that updated page no longer has a URL which identifies it. This breaks HATEOAS badly. The idea of REST is that every state on a site has a representation. REepresentational State Transfer you know... So while there are many other ways of shooting yourself in the foot when designing a REST website, using Ajax makes it almost inevitable.
I'm wondering if bookmarking state would have made it into webapps had we not been forced to use HTTP because that is all that was available in the browser for years.
Huh? You are supposed to correctly choose the HTTP verbs and URI path precisely so that HTTP semantics apply.
If you are talking about page state then there are numerous ways of dealing with that - one example is http://diveintohtml5.info/history.html
If your assertion is that developers can write bad code, abuse HTTP semantics, defeat caches, break navigation etc then so what? With the ability to do things right comes the ability to mess them up.