I'll play. I worked at a financial institution for several years. On the one hand you'd think we were secure because we used a relational database, but we also had a heavily segmented network with all of the databases in their own VLAN's with highly restrictive permissions. On top of that each application was locked down to exactly which data it could use and what could be done with that data.
So if you buy the premise of the article, it wasn't NoSQL, so it must have been secure. In reality we were very secure from external breaches, at least as secure as you can reasonably be.
Personal information was secured to the maximum extent possible. Encrypted, backed up to multiple independent tapes stored in separate locations etc. On the other hand, the overall complexity of the system was very high and if someone breached our network there would have been a very large surface area to attack. I didn't feel like the article addressed this aspect of security in the least. Security just isn't one of those things that are easy or are ever done. It takes constant vigilance and continuous adjustment and improvement.