NoSQL/NoREL is a tradeoff of features for performance. If you don't need certain features and you can make the trade and need the extra performance than it can make sense for some people. I don't think it applies to everyone. They made the decision that was best for them and congrats on that.
Also I can say rotational disks may not provide the economics that make RDBMS seem attractive—but FusionIO cards have really changed that. And I didn't just read the datasheet and get a nerd boner. I watched the queries from 8 beefy physical database boxes (that were getting hammered) combined onto one physical box that was identical in all ways except it had an FusionIO card. It handled 8x the number of queries with ease and could have taken a lot more punishment. Yes, the cards are expensive but in the scheme of getting rid of 7 servers it was actually saving significant amounts of money.
Also I can say rotational disks may not provide the economics that make RDBMS seem attractive—but FusionIO cards have really changed that. And I didn't just read the datasheet and get a nerd boner. I watched the queries from 8 beefy physical database boxes (that were getting hammered) combined onto one physical box that was identical in all ways except it had an FusionIO card. It handled 8x the number of queries with ease and could have taken a lot more punishment. Yes, the cards are expensive but in the scheme of getting rid of 7 servers it was actually saving significant amounts of money.