This. I don't understand why this isn't mentioned more often. Developer convenience and productivity are important things, but the future integrity of your application shouldn't be compromised for either.
There are legitimate usage cases for a non-relational document store like MongoDB, but I suspect there are a non-trivial number of people using it that would be better served by a relational DB. Or even something like Postgres that has both relational and non-relational capabilities.
It's not easier than nothing. You don't have to do ANYTHING in mongo. In any reasonable sized web app with a well designed ERD changing is going to result in you stopping coding and doing some ALTER TABLE, DROP INDEX, etc commands before you can start back with the coding.
Also when you want to create a report you can just write a script aggregates the data and fills another collection on the fly without creating the table first. You can even try out 6 different reports at the same time, without issuing separate create table statements.
It's easy to change a relational schema if you understand relational databases. If you don't then Mongo et al. look like good ideas because they solve an actual developer problem: ignorance.
