The uselessness of PoW outside of the context of the blockchain is actually not accidental:
https://bitcointalksearch.org/topic/an-answer-to-perceived-uselessness-of-pow-hashing-neutrality-855520
This is what makes money system neutral towards any type of useful work.
I don't think comparison of money system to a stock market is appropriate. Money system is a playing field, which needs to be simple, neutral and robust. Stock market is a competition of various players within the money system.
Mining allows competition of control to stay an open game for as long as innovation can occur (indefinitely).
Other schemes would tend towards concentration of control with long lasting network effects.
This is in fact a very intelligent point. I have to say that I was first attracted in principle to such things as primecoin, because they solve at least some obscure mathematical problems during mining. But you are right that what constitutes "useful work" is part of what the market has to decide, and will change over time, so it would be silly to cast it in stone in any successful cryptocurrency.
That said, there is indeed a fundamental difficulty with PoW. In order for it to make the blockchain safe, a lot of work has to be done. On the other hand, that is a cost for the use of the currency (a kind of tax on its usage if you want to). During the early mining phase, that tax is essentially paid for by inflation (the phase we are in). Later, the tax will be the fees that have to be paid.
If it is true that the cost of PoW is comparable to the inflation right now, that is, 10%, now that would be terribly huge. As long as bitcoin adoption is growing, that's not so much of an issue, but imagine that the whole world economy is taken over by bitcoin. It would mean that 10% of the world economic resources would go into PoW ? It is what I touched upon in that other thread https://bitcointalksearch.org/topic/the-bitcoin-moon-and-ecology-865870
I have no idea how much world resources are spent today to the fiat banking sector (I don't mean, how much money the banking sector is handling, but how much the banking sector's functioning is costing: salaries, real estate .... of banking and financial institutions). The cost of the fiat banking sector is the fiat equivalent of the economic cost of PoW for cryptos.
Thanks for understanding!
I would like to compare mining to gaming. Imagine the number of graphics cards sold annualy (tens of millions) and the amount of energy humanity "wastes" on shooting aliens in video games. Nobody seems to complain about that, as there is a lot of fun there. Plus there is an added benefit - gaming led to the development of highly efficient parallel processors that now contribute to research in other areas of human life.
The same way, mining has a lot of fun for nerds building custom rigs and playing with various settings, while manufacturers and vendors push state of the art silicon technology to produce the most efficient machines. Mining might become an incentive for humanity to push research in energy-efficient compuattion, development of new types of energy sources as well as deeper understanding of cryptographic hash functions. So it's not all that useless as it seems on the surface.
Competition requires energy, you can't change that. The good thing, is that energy is not actually "wasted", just transformed.
Interesting point re. all the graphic cards sold.
It would be a great point if those graphic cards were running at maximum energy consumption 24/7 during their lifetime, and if that energy consumption was anywhere close to today's ASICSs.
And if those graphic cards were used to fill giant aircraft hangers, like so:
And yes, energy is never wasted, only transformed. Because first law of thermodynamics. Good one
Beautiful pics
Actually, I would be interested to know the estimates of energy consumption in gaming versus mining.
I don't have the data, but something tells me that the former is orders of magnitude greater than the latter.
Bitcoiners' community is just a few millions in total and only a small part of it crowd-funded mining operations, including those of Asicminer, Avalon, KnC, BFL and others. Gamers, on the other hand, are in hunderds of millions worldwide if not more.
Anyways, competition is fun, it's worth the energy.