Anyway, I've used and have used both kinds of data stores. They have their places. Solr's a great document store with a very good distributed data story, for example. Not to mention interesting nested documents & queries features.

For the most part though, you'd have a hard time convincing me that MongoDB or COuchDB (or whatever other document stores) are good enough as the system of record for actual products.

Yes, relational databases require a lot more thought about your data. That's the point.