I'm certainly not an authority on the app, but, have used it. I believe it is just providing the user name database as a developer quick start (place to create ddl outside of system database).
If I remember correctly, it can safely be removed and/or new databases can be created but you may have to adjust configuration for the quick launch shortcuts for psql or similar.
I installed PG on a Mac using the Postgres.app and I noticed that a database named after my username is created by default. What's the point of this database? Should/can you delete it? Should you leave it alone?
