There's a complaint here
http://archives.postgresql.org/pgsql-general/2011-05/msg00714.php
about the fact that 9.1 pg_dump always dumps CREATE EXTENSION commands
for all loaded extensions. Should we change that? A reasonable
compromise might be to suppress extensions in the same cases where we
suppress procedural languages, ie if --schema or --table was used
(see "include_everything" switch in pg_dump.c).
regards, tom lane