> And even if bitcoin itself fails, I think the blockchain will be one of key technical innovations of this time period. A blockchain is only useful if it is heavily secured by hashing power. This is only the case if there is significant mining equipment devoted to validating blocks. That in turn only happens if there is a reward for validating a block. Long story short, it's currently very difficult to use a secure…
Or not? Proof-of-stake is arguably better than Proof-of-work. Peercoin, NXTCoin and so forth have fundamentally moved forward from the "waste more energy than the next guy" approach that is innate to Proof-of-work.
Peercoin was attacked this way— a miner grinding out alternative histories and finding ones where they were awarded almost every block— _immediately_ when POS mining became possible on it. The attack was thwarted because PPC has a central control mechanism where its developer cryptographically signs blocks to force the network to accept them over longer, otherwise better, chains... and it was later closed off by requiring POW blocks to select the POS blocks that can mine. (But now, the security of that coin reduces to the security of POW and the security of the signing key controlled by its pseudonymous developer).
See also section 5 of https://download.wpsoftware.net/bitcoin/asic-faq.pdf