> I think an economy that builds on people buying loads of crap they don't need is at least comparatively bad. We certainly seem to have a problem with using more than we need from the planet.

It's an issue with macro economics, not the individual. Sure, having people buy less useless stuff is great, but they all still need to agree on a medium for exchange, else doing anything with currency becomes impossible. Individuals buying and selling goods and services don't make currency markets, money flowing through the exchanges does. Market prices are set mostly based on leading indicators from these transactions. When a currency starts deflating, these numbers start looking bad. This is when things start to snowball. Currency worth more tomorrow than today? Stop exchanging BTC for USD(or any other currency). Investments going south and BTC doing well due to scarcity? Then pull out of the markets and hoard BTCs. Market crashed? Get all your BTC out of the bank. At a certain point it all falls apart and everyone is left holding worthless digital currency. This happened before with the great depression and has been studied in great detail. Hence the movement away from the gold standard. Again, very little of this has anything to do with buying TVs and stereos(micro vs macro economics). People don't really need currency to do that anyways. Currency is needed for the exchange of derivatives(specifically debt, AKA loans).