[pkolaczk]

Additionally, when you do a startup and it succeeds it is already too late to redesign your app completely to make it scale. Changing the RDBMS in the middle of the game and migrating data is risky and would cost you probably more than using a properly scalable database right from the beginning.

Additionally once you know you need to scale, your competition will see your product. Knowing the idea works, if they start from scratch, but using a better database for the job, they can easily put you out of the business, because instead of competing and adding new feauters, you'll be busy fighting scalability problems.