Well I would say reconsideration is always right but it's expensive (nosql->sql is big deal) when you are a fast-paced startup and don't want to spend resources on non-critical things. I know it will get critical someday, so we are slowly finding a solution to it.

Schema design allows you to grab stuff you want joined all at the same time (aka the data lives together in a document) in mongodb's model. This obviously has limitations in many to many relationships where the access pattern isn't clear, but often these tradeoffs can work.