PostgreSQL uses the username for a salt when generating passwords, which makes it easier for remote attackers to guess passwords via a brute force attack.
http://marc.info/?l=bugtraq&m=111403050902165&w=2
http://marc.info/?l=bugtraq&m=111402558115859&w=2
http://archives.postgresql.org/pgsql-admin/2002-08/msg00253.php