I didn't. It wasn't subversive, like the parent comment. It just worked out that way because of technology acquisitions. Customers wanted to hear their data was "on Oracle."

My take is that the overhead of maintaining and using Oracle means that you have to cut resources somewhere else. I'm pretty sure a competent DBA and developers can ensure atomicity and integrity using Postgres (instead of Oracle), and have a lot of time left over to create more features in the application.

Don't get me wrong - Postgres is awesome and I would happily use it for any project. I'm not sure Postgres is easier to manage than Oracle and places any less maintenance overhead, but YMMV.

Its just that RAC is a special technology with no equivalent on other DBs. It is usually placed where you need load balancing on the DB level. It normally has very high availability that is a good fit for mission critical DBs. I hate seeing good technology wasted, but you are right that if Postgres is already there and works well, there is no point in moving anywhere.