Good point, but you have to consider that if we're talking about a scenario in which it's being used in the place of a national currency, the bigger picture matters less. If your paycheck can lose 20% of it's value in a few days you may not have the option to wait for it to possibly regain that value. Even ignoring the short term issues, I'm not convinced Bitcoin is any more protected from becoming totally worthless than any given fiat currency. I just can't see the scenario in which it solves or even helps the issue of hyperinflation in a way that fiat currency couldn't.