I want to be clear that I wasn't disagreeing with Ian at all. I think he's absolutely spot on that the dispatching on method shouldn't be done at the WSGI level. It should be done by some layer that's on top of WSGI (I use wsgicollection for that, and it rocks).
The point that I was making was just that GET and POST are not interchangeable. They are completely different operations with different semantics. Adhering to standardized semantics isn't B&D, it's just interoperability and it lets you make simpler clients and servers.