Well, it seems like having a certificate from a CA not in most people's browsers...

protomyth on Dec 17, 2010 | parent | context | favorite | on: Publishing PGP Keys in the DNS

Well, it seems like having a certificate from a CA not in most people's browsers, each of these methods described in the original article http://www.gushi.org/make-dns-cert/HOWTO.html require work from the user and aren't supported out of the box.