One issue, for me, is that as soon as you step out of the realm of GET and POST you start needing to content with proxy servers that are doing stupid things and

One issue, for me, is that as soon as you step out of the realm of GET and POST you start needing to content with proxy servers that are doing stupid things and misconfigured - you also bump into the issue that for some inconceivable reason HTML forms are still restricted to only supporting GET and POST methods. I've written GET requests with bodies and, while they're normally not that useful, if you've got a big chunk of serialized data in the request (i.e. some random blob of JSON with config settings) then they're a reasonable solution. QUERY is nice, but GET is known and, when talking about the web, old standards are a lot more trust worthy.