David is the author of Attack of the 50 Foot Blockchain: Bitcoin, Blockchain, Ethereum & Smart Contracts and, most recently, Libra Shrugged: How Facebook Tried to Take Over the Money.
I've actually known David for many years, having slouched around the London alternative scene with him in the early 2000s when we could both still hack the pace. These days, he's a systems administrator for a publishing company. He also spends an awful lot of time on Twitter refreshing the page and commenting on crypto topics. It's fair to say that he's a sceptic about all of this stuff ... he's not convinced that there's any real merit to Bitcoin as a currency, that business blockchains solve any problems that can't be solved in other, better ways, or that smart contracts are either smart or contracts.
You can catch up with David on Twitter