>it would be profitable for Bitcoin miners to burn through over 24 terawatt-hours of electricity annually

So 0.02%[1] of the global per annum energy consumption? <snore> I'll gladly trade that to run an economy without violence and bring financial inclusion to 6 billion unbanked people.

[1] 24/109613*100
https://en.wikipedia.org/wiki/World_energy_consumption

>Because you don’t need permission to buy hashing power and participate in Bitcoin, there’s no way a “51% attack” can be stopped, except by outbuying your competitors

Incorrect, this author doesn't understand the miner<->node relationship. Miners do what users value or else users change the consensus system they value. DoubleSHA256->Script or Equihash etc etc

>In Bitcoin, acceptance of a change is signaled by the miners - once some percent of the miners agree, the change is accepted. This means that hashing power is used as a measure of voting power, and so the political system is essentially plutocratic.

Incorrect again. The author is mistaking how consensus-level changes, that users want, are coordinated among miners. BIP 9 was a method where users said "we'll wait for you all miners to coordinate amongst yourself a consensus change" which was used to delay. In the future Bitcoin will use BIP 8 which is "Miners prepare to have your old consensus rejected at flag point X or else your blocks will be orphaned.

>Bitcoin has been wildly unstable, with controversies and forks happening quarterly.

The bitcoin network is stable as a table. Bitcoin can't deny anyone from creating their own fork from consensus. This is a critical feature not bug, to be able to easily exit from the system. It prevents lock in that plague trusted third parties.

>I’d explain proof-of-stake here, except that I don’t totally understand it yet.

If you don't understand the second most prominent proposal for decentralized consensus, why are you writing a critique about blockchains? PoS is inherently broken from an economic perspective because it is no more "efficient" than PoW. Marginal Cost = Marginal Revenue.

If you have an incentive mechanism that says, "Do X and you get Y money" you're going to spend X<Y amount of economic work to get Y money. http://www.truthcoin.info/blog/pow-cheapest/

PoW = destroy X value in fiat space to gain Y value in Bitcoin space
PoS = destroy X value in Ethereum-PoS space (via TVoM, meat-space work) to gain Y value in Ethereum-PoS

The value in PoW is that it's very hard to 'more efficiently' consume electricity than your competitor. All that PoS does is push that wasted work into hidden area or human space.

>Instead of a network of miners, you use a single host. That host maintains a secure ledger which contains the host state and its activity log, including all requests and their results. That ledger is then published for clients to actively sync and monitor.

Ah, So digicash. Which when it went out of business the market died because there was no coordinator any more to check double spends. Let's assume that the business never can go out of business. If I want to destroy the network, I can compromise one system and control the entire state of the database. Ok let's assume the system is uncompromisible. Oops the state just censored your 'secure' ledger because someone did something with it that the political class didn't like. "We'll host it in a country with 'just' laws" There is no such thing as "the public good" where all people benefit from a certain action. There will always be winners and losers in any policy decision. Now value is sapped from the system by constantly having to pay lawyers to defend your rights from encroachment by the state.

The author is right to question if everyone application needs to run on a blockchain (hint: they don't). But if you need trustless, robust, decentralized, uncensorable state to be agreed on by multiple parties, you're gonna need a blockchain