The U.S. Postal Service has not yet failed, probably due to the lack of a directory. It has problems, but lack of a user directory is not one of them. There are zillions of mailing lists that facilitate the spewing of tons of junk mail on all kinds of people. It's hard to imagine how a national USPS public user directory would benefit us. Consider the Internet.
Chaos reigns supreme.
The Internet has been doubling every year without a comprehensive directory other than the need for a directory of technical and administrative addresses for all connected domains. Get rid of the gateways, and the need for the directory will largely disappear. The IETF has played a major role in the past and will continue to do so. The IETF provided a vendor-neutral ground and technically sound development and review processes that made the unprecedented industrywide adoption of LDAP possible. The IETF will continue to play an important role as LDAP evolves, even as the market begins to drive development of the standard.