[TeMPOraL]

> Why do you say that? it would just change the total equilibrium expenditure on mining, not render it pointless, since the blockchain just has too be too expensive to attack, and the same constraints would apply to attackers and miners.

I feel it would significantly slow its growth, perhaps making it not worth the while relative to alternative solutions.

Also, the way I understand it, PoW has its growth limited only by a) how fast can you provision the hardware, and b) how much energy you can throw at it. I worry that we'll never arrive at the point of having clean energy too cheap to meter, if we have a black hole fueled by pure, refined greed, which can suck all the energy surplus pretty much instantly.

[SilasX]

Mining expenditures are limited by the benefits relative to the cost. Increasingly expensive mining is added until the expected revenues of bitcoins sold don't make up for them. At the moment right now, more mining could come online, but isn't taken online because it wouldn't pay for itself.

If energy becomes more expensive -- say, by pricing in the externalities of some energy sources -- that decreases the equilibrium expenditure, because marginal mining can't pay for itself anymore.

The concept of "pricing out miners" doesn't even make sense to begin with. Miners are competing with other miners (including malicious ones). Any resource constraint affects all of them; it can't make all of them give up. To the extent that other coins become popular, that (again) just prices out marginal miners.