@b0rk sqlite is just such a good idea.
I've never really understood why _all_ databases don't come in a form that runs as a library. Any time you want a db that's only accessed by a single uid, it's a huge inconvenience to run a db server in a separate account and then manage a username and password for the app to log in to it.
If all dbs had this mode, I'd be able to choose 'server or library?' _and_ choose the db whose feature set was best suited to my application. I'd love a libpostgres!