If you can have similar or better security properties as mining without the cost incurred by the competition of energy expenditure, then the mining is wasteful.
While absolute trustless history seems good, it has a significant drawback as well: it isn't anti-fragile. That is, there is no way for the network to become stronger after recovering from a double spend attack, e.g. by slashing stake of the attackers.
You don't need long-range fork protection as long as the expiration of a block hash is known in advance. That is, short-range fork protection is all you need as long as the range is long enough -- e.g. a year. And this can be done entirely without mining.
This is simply wrong. When presented with a valid history and a simulation how do you tell them apart?
Vitalik says cryptocurrency developers should "reach out to LessWrong more", in order to not be ignorant of advanced computer science and game theory topics.
https://blog.ethereum.org/2014/12/31/silos/
I think Vitalik raises several major important points, namely:
* Bitcoin's $600 million wasted on electricity yearly in order to secure the network is a huge problem. Various Proof of Stake algorithms are attempting to improve upon this. The ideal solution would be one which combines the low cost of the Proof of Stake algorithm, with the high security or Proof of Work. I not enough of an expert to be able to say which solution is best, but both the Ripple consensus algorithm and the Bitshares Delegated Proof of State algorithm look promising. I am interested to see what algorithm Vitalik will choose for Ethereum.
* ASIC miners are a problem due to the resulting centralization. They have also lead to increased centralization in Bitcoin, as the network is now increasingly controlled by a few large mining pools.
* Blockchain technologies have a great potential to change the world, and solve governmental and organizational problems that society is facing. Beyond simply revolutionizing money, blockchain technologies could also be used in the future to support prediction markets, voting/consensus building, exchanges, etc.