Re: Replacing Bitcoin with something less wasteful (split from Is deepbit.com stealing coins?)
It is good engineering practice to seek energy efficiency. It's not just good, it's expected, it's not optional any more. It's hard to believe that an open-ended energy requirement was anticipated in the design of bitcoin. There may have been some rationale about increasing powerful and efficient computing meeting needs in the future, but that doesn't count for much. If I had a bitcoin for every "it's gonna be great!" thing that was just around the corner and then never came to pass, I would have quite a pile of game tokens, I could use them to buy one of them there jet packs everyone uses to commute these days 
The efficiency of Bitcoin mining hardware has already increased by three orders of magnitudes (in terms of MH/W).
Athlon 64 ~=- 0.02 MH/W
AMD 5000 or 6000 series GPU ~= 2 MH/W (peak 3MH/W w/ tweaking & undervolting)
45nm FPGA custom miner ~= 20 MH/W
The desire for more efficiency (and thus higher profitability) will continue to drive efficiency gains. There is no open ended energy requirement. The annual revenue from mining puts a limit on the expenditures for the network. If anything as time goes on the move towards FPGA (higher capital costs and lower energy cost) which further limit the energy cost to maintain the network. Personally I think the network is overbuilt by a factor of 2x to 3x but as mining becomes a lower margin operation I expect some marginal miners to continue to idle.
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Consequently, the best case expectation is that progress will replace bitcoin with something that addresses its shortcomings, both technical ( for one, it's an energy pig ) and behavioral ( de facto centralization of its operations in currency exchanges and other institutions cloned from the bad world some would tell you that bitcoin will replace ).
Then propose one. The problem is non-trvial. How do you acheive consensus in an anonymous network?
The proof of work is the method Bitcoin uses. If you believe there is a superior method THEN SHOW IT.
You just went on a rant.
Bitcoin is inefficient BLAH BLAH BLAH
There is a better way BLAH BLAH BLAH
I can't tell you what it is but Bitcoin sucks.
If that is the extent of your contribution then the logout button is over there.
Bitcoin is inefficient compared to a centralized network. Satoshi even discuss that inefficiency in his paper. There may be alternatives but YOU haven't proposed one. The cost of the Bitcoin network (both hardware and energy) deters an attacker. A security guard at a bank which doesn't get robbed is equally inefficient. It is one component of the costs in that system (physical money). There may be other ways to deter an attack with lower cost but so far you haven't shown one.