The difference is that for most goods, the marginal cost of production falls with increasing economies of scale. Bitcoin is the exact opposite: The block difficulty will continue to escalate as more miners enter the market. It's like running on a treadmill that keeps getting faster and faster. Oh, and instead of making you healthier, your treadmill pumps more and more soot into the air around you.
Yes. A bitcoin is basically a token that says that someone, somewhere has wasted a (quite large) amount of electricity on your behalf. It's an incredibly pure form of conspicuous consumption.
(Likewise with gold you know there's a pile of acidic tailings and a river full of arsenic to back it up, and with diamond mining quite a lot of real human suffering)
Though it's never wasting. You can phrase it better by saying that:
A bitcoin is basically a token that says that someone, somewhere has spent a (quite large) amount of electricity on your behalf to make sure that your bitcoins are secure and safe.
(The more computing power used, the harder it is to counterfeit transactions.)
The actual computation done is not computationally useful. It only "secures" your bitcoins in the sense that an attacker has to put more economic input into their attack to match the economic input of the mining network. The act of mining does not even check whether the transaction is valid - that is done by the host that decides which transactions to include and the rest of the network deciding to propagate a mined block. Mining just churns through a single hashing algorithm to deliberately expend power. You could also secure your network by introducing trust and actually securing the trusted nodes, without having to create an ecological travesty.
Except those computations aren't actually doing anything useful. They're not protein folding, they're not analyzing data, they're just computing for the sake of computing.
