Let me play Devil's advocate here. I'm not sure why people assume that just because they are familiar with how to allocate names in a particular name space, that that name space should then be adapted to every purpose that comes to mind. There is value in having semantics associated with a name space - a value which is diluted by using that name space for a wide variety of purposes. DNS is too overloaded as it is. Beyond that, DNS is not well-suited for media types. DNS assignments are ephemeral. They are subject to change as their assignees (e.g. the organizations whose names they reflect) merge, split, go bankrupt, fail to renew their registrations, or sell off trademarks. They are subject to reassignment for arbitrary reasons. We discovered long ego that URIs based on DNS names are not suitable for long-term (archival) use precisely because those names change; that's why URNs and DOIs were invented. And the utility of URNs has been nearly destroyed by misuse and overloading of that name space. It must be questioned whether it is beneficial to the public to define new media types on a whim anyway. The failure to pay proper attention to the design of media types, the failure to do security analysis of media types, and the failure to respect those analyses even when they are done is the reason why email- and web-borne viruses and worms cost billions of dollars to consumers. If there really is a compelling need (meaning that it serves the greater good) to define new media types at a whim, a much better set of names already exists, one which was more-or-less designed for that purpose. It's called OIDs. They are easy to obtain. They are recursively extensible just like DNS names (actually moreso). It is relatively well-established that once assigned, the meanings of OIDs do not change. They don't contain human-readable content that invites disputes over ownership. The argument for DNS media types reminds me of countless other arguments for why protocol X should be used for everything (or at least, every instance of some large class of problem). In the past X has taken on values such as SOAP, XML, HTTP, SNMP, LDAP, URLs, SSL, ASN.1, RPC, and even TELNET. Most of those arguments look pretty naive now, but people took them seriously when they were in fashion. Now it's essentially being argued that since DNS is a widely-deployed namespace and query protocol, that it should be used for yet one more thing that could be looked up. Keith p.s. gratuitous analogy to a famous quote: Abraham Maslow is supposed to have said "It is tempting if the only tool you have is a hammer, to treat everything as if it were a nail." I like Mike O'Dell's version better, which I'll parphrase since I didn't manage to write it down at the time: "If you need to drive a nail, the fact that you have your forehead with you doesn't make it a good tool for the job."