Database(s) per instance ?

Can anyone site any advantages to having more than one database per ORACLE instance, other than saving shared memory (SGA) ?

The UNIX administrators here want me to include ALL of my DBs in one instance. Currently, I have two medium-size DBs and one little data warehouse which someday will become a big warehouse.

I tend to find more disadvantges than pluses: single point of failure if instance dies, taking database down for maintenance effects ALL apps, not being able to taylor an instance to a specific app, etc.

Thanks,

--
 Tom Gillespie                                                 -   -
 Harris Semiconductor                                         | | | |
 Manufacturing Systems                                       _/\/\/\/
 Palm Bay, FL                                                 | | | |
 Tom.Gillespie_at_harris.com                                      _   _