Taking all these comments into account, if startups have to prototype quickly while trying to find market fit, does it makes sense to start off using something

Taking all these comments into account, if startups have to prototype quickly while trying to find market fit, does it makes sense to start off using something like mongodb but with the plan to migrate to another database when you business starts growing? The database space is so confusing right now. It seems like Postgres is the safest choice and i also like this post fron Adam D'Angelo - 'http://www.quora.com/Quora-Infrastructure/Why-does-Quora-use-MySQL-as-the-data-store-instead-of-NoSQLs-such-as-Cassandra-MongoDB-or-CouchDB http://www.quora.com/Quora-Infrastructure/Why-does-Quora-use...