Can you give a concrete example where MongoDB blew an RDBMS out of the water in regards to prototyping? I find that database schemas don't really get in the way until a project matures, and then it becomes a road block both in a legacy manner and that making changes puts strain on the database infrastructure.
I can't remember the last time a schema I made in week 1 was similar to the schema in week 4. That alone is why I made that statement. Modifying schemes requires modifying code all over the place that relies on it. The majority of the time, with Mongo, I can ignore those changes and only code for what I added.
That is my experience. Perhaps you have the patience and foresight to plan out your schema well before coding.
