I've actually done what this RFC proposes twice before simply by configuring my DNS server carefully. Once I left an open wifi AP at a tradeshow that served our company's website regardless of the domain entered. The other time I specified that all hosts used the address of our proxy-filter so that there was no need to configure a proxy server on your computer.
I'd have to think it through a bit but I think these techniques would work on a larger scale (like a country). Perhaps I'll write an article about these unorthodox DNS configurations if people are interested.
