Sheesh, what's with the MongoDB witch hunt? It seems like HN can't go 2 days without some disparaging of MongoDB. I get it. I'm an idiot for using MongoDB even though it suits my needs perfectly.
I really don't see that the author put forward a convincing argument. He seems to be stuck in the 100GB data blog post, but he confuses NoSQL with literally "don't use SQL", which is really somewhat missing the point of so much of this space.