I don’t know if we are ready for that sort of thing. But Justene Adamec is inclined in that direction and is soliciting your views over here.
Here’s my take on this idea. First, I don’t think you can get sufficient consensus on what is proper blogging behavior (e.g. how much should you edit a post after publishing it?) that you could ever wind up with a set of statements that you could properly call a “Code”. Maybe you could get enough people to agree on some “guidelines.”
Trying to create a “Code” seems a tad ambitious but, hey, what do I know?