tablespaces and DB administration

Now that it looks like tablespaces will become a practical reality, I want
to suggest some changes in documented procedure and preferred setup. The
reason why I suggest these changes is to enlighten new PostgreSQL users to
the new features and, perhaps, make a more enterprise-familiar environment
for experienced DBAs.

First, we keep the standard PostgreSQL directory the way it has always
been with template0, template1, pg_xlog, pg_clog, etc. in the same place.
We can refer to this as the "system" directory. This makes sense because
all the system level stuff is there. User databases should be discouraged
from the system, and users should be encouraged to create and use separate
tablespaces for their databases.

This is usefull for a couple of reasons: 1st, it makes monitoring database
size easier while also simplifying xlog monitoring, as well as makes a
logical separation from the PostgreSQL operational core and its external
data. 2nd, this is very similar to how other databases view data.

What do you all think?