[andrix]

I think it's not a fight. RDBMS has been there for many years and they have proved to work in many areas. NoSQL databases born for new needs people was asking to have in their new projects. Both would probably works perfect for many cases, but nosql databases are very suitable for scenarios when you do not require an strict schema, and also they are simple to setup.

I still think MongoDB is great for many applications as many companies are using it for their data needs (like Foresquare), and the same with RDBMS like MySQL, that lot of big fishes use them for different parts of their architecture (facebook, twitter, etc). In the end, each option has pros/cons, but one will be better for your use case.