#tcpip_socket = false
and must be changed to
tcpip_socket = true
to allow TCP/IP connections, even from applications on the localhost.
This is rather annoying, and difficult for non-technical users to do when
installing applications such as Glom. By the way, debian activates this by default.
This is following the default upstream behavior, which I'm disinclined to have
the RPM editorialize on in any significant fashion. Loosening the connection
restrictions from what users expect from the PostgreSQL documentation could
result in unexpected security holes.
FWIW, Postgres 8.0 does allow local TCP connections by default, so FC4 will act
the way you want. But I think it's a bad idea to change it in FC3.