Some data is just relational and works better when normalized and properly stored in a rdbms.  This is especially true for data which you might want to give ad hoc reporting capabilities to.<p>So yes, we use both relational and nosql and both have their place.  My 2 cents is start with the data, figure how and who the consumers are and how to best structure data for them then pick the most appropriate database.  In some cases we have data start in mongo and then it gets processed further, refined and then ultimately dumped in MySQL for reporting and ad hoc queries.