[achompas]

Money supply needs to be a flow, instead of a stock, so that it can adapt efficiently to supply and demand and change with population and economic output.

The entire system could thrive on one bitcoin.

No, it couldn't. One bitcoin could not sustain a currency market, and a one-bitcoin market would value that bitcoin at highly variable prices.

[derefr]

But you can have half of a bitcoin. In fact, they're divisible to 8 decimal places—so, in reality, when you have "1 bitcoin", you actually have ~10 million atomic units of tradable currency. It just comes "pre-redenominated," because it currently lacks value, and may be redenominated downward (making the unit "bitcents" or somesuch) as the exchange rate increases.

[WReckus]

1 Bitcoin can be divided into .00000001-sized pieces and traded separately. You couldn't run out if you wanted.