Yet another failure to understand the purpose of mining. The energy is NOT being wasted. In fact, the energy spent mining is the exact thing that makes the Bitcoin network function. The energy is being converted into trust. The more energy that is spent on mining, the more difficult it will be for a well-capitalized entity to perform an attack on the network.

Aaron Greenspan, repeat after me: Mining energy is not wasted. Mining energy is not wasted. Mining energy is not wasted.

Now, it is an open question as to whether the cost of running the Bitcoin network is worthwhile. However, for the moment, it clearly is. The fact that some miners can turn even a small profit on the Bitcoins they're rewarded with demonstrates that the utility they provide has positive market value.

Of course at some point it may be that it costs substantially more to mine new Bitcoins than they are worth on the market. If this happens soon, Bitcoin will likely fail. If it happens later, it's possible that transaction fees could prop up the network, but that's purely speculative.

Another thing to consider when assessing the energy efficiency of the Bitcoin network is how it compares to the efficiency of existing currencies. Cash has a physical component and must be manufactured. Electronic fiat is backed by huge, complex, and expensive networks. Visa's datacenters are not free. Keep in mind that credit card transactions typically have a transaction cost of 3%, which in some way represents the cost of operating the Visa network. 3% is kind of a staggeringly huge number, and off the cuff I expect that's actually quite a bit higher than the total Bitcoin network cost to volume ratio...