The databases of user me live in /home/postgres/me/. We use the new PostgreSQL's "tablespace" mechanism to make this more elegant than the MySQL set-up. Tablespaces are named containers for databases that are associated with particular roots in the filesystem. We give each user his own tablespace, with the usual ownership by his group, setgid, and no group permissions. me can't modify the database directly in an effort to confuse or crash Postgres; and, of course, all database files are counted towards me's group quota.