Who really needs this for their web app? Nearly 99% of heavy web apps require a login, so Google is out of the picture anyway. Anyone who is building a content site with DOM-manipulating Javascript doing all the work have completely lost their way. Seriously, just render your templates on the server and deliver them to the client. Why does the world want app-ify everything?
Because server architecture and rendering is really expensive to scale whereas a client-side-dependent app could be supported for much less. It is a trade-off. The presentation layer has been moving to the client-side for the past few years, where have you been?
I've been keeping up like any developer, in fact I'm writing a Backbone app as we speak. But like all of the apps I write, Google doesn't need to crawl it.