If I was Netflix I would de-cloud, but if I was a small team like 37signals then de-clouding is just insanity. I think DHH is either very stupid or extremely naive in his cost calculations or probably a mix of both. Hey and Basecamp customers will see many issues in the next few years and hackers will feast off their on-premise infrastructure.
They’ve had non-cloud infrastructure for a very long time. Their new orchestration methods notwithstanding, reliability and security are unlikely to suffer.