Performance is definitely an important aspect, but coming from a background working at smaller companies, bootstrapping time and development time are a factor as well -- and while Postgres is easy to set up if you're familiar with it (and I dare say it makes DB design fairly straightforward), Mongo and other NoSQLs are pretty objectively easier to just get working if you aren't fluent in relational databases.
No offense, but if you don't know how to design/develop a database schema, making it easier to shoot yourself in the foot by using NoSQL database is not the answer.
None taken. And I agree -- but database design is inherently different under SQL and non-/noSQL. Constraints and relationships may be modelled completely differently in either case.
