>Scarcity is also not something that you want from a currency, fundamentally. A currency needs to be abundant when needed, and scarce when oversupplied. That's the point of controlling the money supply based on economic growth rates, and the entire reason we have a Fed.

Yes, we mold the currency to our needs, that's why we have abandoned gold. This is one of the reasons the euro is completely flawed. Each eurozone country has different needs, yet there is only one currency that can only be controlled for the eurozone as a whole. Without further political integration it is not possible to actually give each country what it needs. Some countries need a weak currency, some need a strong currency. Paradoxically, the euro is both too strong and too weak at the same time.