[runeks]

> Proof-of-work is simply not sustainable (energy-wise), IMO, for the foundation of a global system. The stability of whole ecosystems is predicated upon those ecosystems being attractive to people who want to make money by competing to solve hard problems by brute force.

What do you mean by this, exactly? Bitcoin miners look more than willing to earn money on brute forcing hard problems.

The point of proof-of-work is that it shouldn’t matter what anyone thinks about it. It’s basically impossible to ban (anyone can do a SHA256 calculation), and the difficulty automatically adjusts. In addition to this, the block reward — currently 12.5 BTC per block — halves every ~4 years, so less and less electricity will be consumed until only transaction fees provide capital for proof-of-work[1].

[1] http://www.bitcoinnotbombs.com/wp-content/uploads/2014/06/37...

[andrewstuart2]

I mean that to stay stable and grow in popularity, bitcoin must sustain ever-increasing energy demands so that nobody has a majority and can start double-spending. The whole goal with variable difficulty is to counteract the ebb/flow in popularity and ensure that the work takes ~10 minutes. This ensures that as the popularity grows, more energy is required since it will always take 10 minutes for a new block, regardless of how many contributors are involved.

Furthermore, the miners are here for the direct mining rewards. I think the future transaction fees approach will be significantly less attractive, so I'll be very interested to see how that change plays out once the era of rewarded mining is over.

[rocky1138]

The difficulty you mentioned only applies to certain currencies. Ethereum, for example, has a built-in "difficulty bomb" set for later this year to make hashing essentially unworkable.