a) use DNS for finding URN resolution services
(cf. various draft-ietf-uri-urn-* proposals).
Among other things, URN resolution services would help you find mirror
sites and replicas of the 'same' resource.
b) use DNS to indicate HTTP-NG vs HTTP support.
Simon Spero mentioned this in his talk describing HTTP-NG, that DNS
records might indicate the use of a completely different protocol for
http://foo.com/path
c) use DNS for simple host replication/round robin to indicate
multiple sites at different geographic (network topology) locations.
Whatever you think of these individually, doing them all with separate
DNS entries seems like a bad idea.