[microtonal]

I don't know. It's a hard question. MongoDB is pretty much used in any hackathons simply because it's easy to setup, driver support is good, and schemaless. The last one is really why people use MongoDB over SQL DBMS.

I find that a poor argument. One can use an ORM that automatically creates a schema based on classes. E.g. I like Ebean with DDL generation. You just write classes and add @Entity annotations. Ebean automatically creates the schema. Combine this with an embedded database, such as h2, and there is virtually nothing to set up.

Once you are out of the rapid iteration phase, you can take the latest Ebean generated schema and use to proper migrations for later changes.