Bitcoin's entire raison d'etre is that its transaction clearing mechanism is decentralized among untrusted parties. The best known way to enforce honest participation in this mechanism is by requiring workers (miners) to prove that they've expended resources (incurred a cost) in order to to be eligible to publish the next block and claim the block reward + transactions fees.
When a miner Finds a valid hash for a block, they prove that they've consumed a certain amount of electricity in a way they everyone can easily verify. In order for someone to perform a 51% attack, they have to use more electricity than everyone else, which is probably more expensive than just participating honestly. The security of the network is proportional to the amount of money it costs to attack it.
Mining is therefore neither wasteful nor inefficient, if it is understood that the goal is to have a decentralized, censorship-free currency that disincentivizes attacks.
> There community around dogecoin is, generally speaking, more amenable to tipping
I disagree with this - Bitcoiners have been quite generous with tipping in the past, and it's been picking up again thanks to the ability to tip millionths of a bitcoin (informally called "bits") using ChangeTip.
MtGox does allow you to withdraw in USD, it's just that you get put on a long processing queue. The problem is that their Japanese bank has restricted them to only 10 international wires per day. They've been having a really tough time with banks. Interestingly, if you have a Japanese bank account, you can withdraw Yen from MtGox within a few hours.
Regarding price - MtGox's has been fairly in step with BTCChina's price. BTCChina and MtGox both represent the top exchanges by 30-day volume, so it would seem to me that MtGox's price is more accurate than BitStamp's price which lags miserably behind every rally.
When a miner Finds a valid hash for a block, they prove that they've consumed a certain amount of electricity in a way they everyone can easily verify. In order for someone to perform a 51% attack, they have to use more electricity than everyone else, which is probably more expensive than just participating honestly. The security of the network is proportional to the amount of money it costs to attack it.
Mining is therefore neither wasteful nor inefficient, if it is understood that the goal is to have a decentralized, censorship-free currency that disincentivizes attacks.