Well, it could define that anything that matches either the syntax /en/ or /en-gb/ is locale information and should be ripped out of the url, which should be a simple regexp. This would only make it impossible to use top-level URL's with that syntax, I don't see a big problem with that.
I have a version of Don's code with the greenpeace specific stuff removed (it only looks for the /en/ syntax yet), which may be useful as a starting point.
