There are different implementations of PoS, some are vulnerable, some are more secure than PoW.
Yeah.
Just because some coins have flaws that have been exploited does not mean that PoS as a whole can be dismissed.
People should be working together to push PoS technology forward as it's clearly superior to PoW. I find it hard to believe that someone could justify the excess of PoW if and when a PoS alternative exists. Other than making an argument for PoW purely out of self interest of course.
Right now PoW is dominant. And there are some PoS currencies like NXT that are progressing well and appear to have a good chance of solidifying their place as the first secure decentralised PoS currency. Time will tell how it plays out, but it's looking good for PoS thus far I think.
It's possible that PoS isn't feasible but so far even for 'Nothing at Stake' attacks, V. Buterin and Come-From-Beyond seemed to agree that there was a theoretical solution. And that seems to be the main issue right now against PoS.
A Nothing at Stake attack was done twice on Navajo, which is a PoS coin. That attacker, since he owned 50% of all navajocoins, can now doublespend, anytime he wants at any time in the future, just because he owned 50% of all coins temporarily....PoS=Piece of Shit.
That's like saying Bitcoin and all other PoW coins are a piece of shit because lukejr 50% attacked coiledcoin a while back.
In a way, but the difference is you can only doublespend on Bitcoin if you have 50% or above hashrate(even then its not 100% that youll succeed), with PoS, you can doublespend when you have 50% coins, and even when you dont have 50% of the coins anymore. So once you get 50%, you will always be able to doublespend, at any point in the future..
That's not accurate with regards to PoW. PoW is far, far less secure than you seem to think it is. See:
http://hackingdistributed.com/2014/06/16/how-a-mining-monopoly-can-attack-bitcoin/Specifically:
33-50%Selfish mining will yield profits above fair share even if Bitcoin is patched. Selfish miner need not be well-connected to the network to win; it can unilaterally earn more Bitcoins with selfish mining. No fix possible, ever.
Double-spends against 6-confirmed transactions are feasible but not guaranteed to succeed. N-confirmations for large N will mitigate merchants' risk.
>=50%
Loss of decentralized trust narrative, inability to differentiate Bitcoin from competing technologies.
Double-spends against 6-confirmed transactions are certain to succeed.
Selected miner targeting: Pool can reject any selected block found by any competing miner.
Selected transaction targeting: Pool can reject any selected transaction and keep it out of the blockchain.
Selected address blocking: Pool can block Bitcoin flows in or out of selected addresses.
Transaction Differentiation: Pool can deprioritize certain transactions and rely on other miners to mine them unless a (hefty) fee is attached.
Fee Extortion: Pool can deny transactions from a particular address unless a (hefty) fee is attached to those transactions.
Complete denial of service: Pool can ignore and orphan every single block found by competitors, thus stop all Bitcoin transactions.
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So starting at 33% a miner can have a reasonable chance to double spend. And 50% is not just a chance at double spending. It's full blown control of the network on many levels as listed there.
