I see the arguments for or against schema-less and transaction-less databases as similar to debates about corporate dress codes. For example, it can be true that allowing *some* employees to wear tee-shirts and shorts into the office can improve worker productivity, moral, etc. But it also depends on self imposed constraints and the the individual's role in the organization. Warehouse workers certainly don't need a coat and tie, but there are different expectations for public facing staff or C level executives.

Likewise, some databases are inherently transactional and are relied upon to be a single version of truth, especially for mission critical things like financial applications. But, yes, if you've got a team in the back office performing sentiment analysis against petabytes of social media feeds, then the focus should be on maximizing turnaround and minimizing operational costs; referential integrity and pants are optional.