Your claim that attacking a PoS coin is a "fixed cost" and attacking a PoW coin is an "unbounded cost" is similarly ridiculous considering the costs of attacking both types are dynamic (PoS depending on the price of the coin and PoW depending on the hash power of the coin.)
It is absolutely correct. Once you control a PoS coin, you control it forever at no additional (significant) cost. How can anyone else ever take control away from you since you control staking and the only way anyone else can get stake is by buying it from you? No one can and you don't need to continue expending resources (mining) to retain control as you do with PoW.
Wrong. If someone buys up 50%+ of the currency supply to attack it, the PoS coin's community thanks them for the donation, forks the coin, rolls back the blockchain, and continues business as usual.
In that case, the system doesn't work at all, because it doesn't enforce consensus. You might as well have "the community" record everyone's holdings on a spreadsheet.
Also, attacking via 50% doesn't necessarily require "buying up" anything. It could be (at least in part) having hacked an exchange or other large holder, or having accumulated stake through borrowing. The same with PoW (compromising a large pool for example), except that it isn't permanent.
Obviously that is not an ideal solution, but a worst-case scenario solution. Feel free to try and attack a PoS chain and let me know how successful you are.
You are missing the point. The stake is an attack.
If you and few others who were Kings before but gave up majority stake, you fork but the users may not follow you. The masses tend to be very apathetic about changing what they are accustomed to.
The majority can change the protocol at-will. Ditto with Satoshi's PoW (
but I claim not in my innovation), except it is an unbounded ongoing cost;whereas, with PoS it is a one-time cost. And you can even recoup that cost by shorting the coin if the manipulations will cause a drop in price, or by recouping profits gained from changing the protocol.
As long as the protocol changes don't too much inconvenience the masses, they won't bother to change. For example, adding a small transaction fee that is paid to the new Kings.
You claim we can't attack PoS, but this may be because there is no profit for us to do so, because your PoS coins have no usership nor sufficient non-mirage liquidity to profit from shorting. Go grow the usership and/or the true liquidity of the float, then observe the game theory.
You are also presuming that the majority of stake exists. Instead you may have 10 coalitions of minority stakes all fighting each other. Thus 10 forks and chaos due to being able to spend the coins 10 times.
Forking will almost always be avoided because politically it is devastating. Again the attackers can just short the coin.
A dictator attacker who unifies control (a la Napoleon) by acquiring majority stake would perhaps be cheered (ending the chaos). This is the strategy being deployed right now before our eyes to bring the world to its knees to beg for a NWO one world government to stop the nation-state chaos. The banksters created that chaos on purpose.
Refuted.