Bill de hÓra points out one of my biggest annoyances with HTML, that it doesn't support a larger complement of HTTP verbs. He does have a different spin on it than I had previously thought of, that because it only supports GET and POST that HTML effectively subsets HTTP.
So, HTML subsets HTTP. If any other technology did that, there'd be uproar. Yet I don't think the W3C Technical Architecture Group have even discussed this. Why does it break web architecture? Well, instead of using PUT/POST/DELETE in a form against a single resource/URI, I either have to use multiple URIS to operate on a single resource, or I have to tunnel the PUT/DELETE actions though the entity. Truly, deeply, absymal.
It certainly is annoying, and this is the kind of thing I'd much rather see the W3C HTML working group work rather than creating non-backward compatible versions of XHTML.