The main problem with the fragment change solution is that it _doesn't work without JavaScript_. And we're not talking for the one user browsing the site - any links people post (on forums, mailing lists, etc.) that have fragments in them are simply unusable for people without JavaScript, as the server does not get sent the fragment - the best it can do is send a generic "oh, sorry, no JS" page back.

This would be a problem for search engines as well, if it wasn't for the awful translation Google said they'd do. It's just breaking the meaning of fragment identifiers completely, and that really makes me worried.