~$ dir /data/02/share | grep datab
  drwxrwxr-x  2 me   postgres  4096 2006-10-16 21:38 database/

~$ touch /data/02/share/database/testing.testing
~$ dir /data/02/share/database
total 8
drwxrwxr-x  2 me postgres 4096 2006-10-16 21:53 ./
drwxrwxr-x 16 me people   4096 2006-10-16 21:38 ../
-rw-r--r--  1 me me          0 2006-10-16 21:53 testing.testing
  
$ psql -U me dupe_filenames
Welcome to psql 8.1.5, the PostgreSQL interactive terminal.

Type:  \copyright for distribution terms
       \h for help with SQL commands
       \? for help with psql commands
       \g or terminate with semicolon to execute query
       \q to quit

dupe_filenames=# \du
                               List of roles
 Role name | Superuser | Create role | Create DB | Connections | Member of 
-----------+-----------+-------------+-----------+-------------+-----------
 me        | yes       | yes         | yes       | no limit    | 
 postgres  | yes       | yes         | yes       | no limit    | 
(2 rows)

dupe_filenames=# create tablespace thisisatest         
dupe_filenames-# owner me
dupe_filenames-# location '/data/02/share/database';
ERROR:  could not set permissions on directory "/data/02/share/database": Operation not permitted