If a currency like Bitcoin that can lose half of its value overnight is better than your local currency, that local currency must be pretty damn bad.
You have to be kidding, I hope. Investing into bitcoins or using it as savings usually means that the investment will stay in bitcoins for at least many months, often years. There has been only 1 month period in the entire history of Bitcoin where the value was actually higher than it is now. That was in June 2011. Investing at any other time would have been profitable, most of the time very profitable.
This doesn't really prove anything for the future but saying that bitcoins are a bad
savings currency is absolutely ridiculous. There is nothing in the whole world that is better right now. The arguments regarding volatility affect a different problem entirely. In the short term or for using bitcoins as a payment method, volatility does matter and it can sometimes cause big problems. This will get better with increased liquidity, however.
These are two completely different issues. Long term thinkers know the value in Bitcoin and so far that has been rewarded in a strong way. Bitcoins don't only store value, they actually increase value right now because there is so much growth. Even a 30% inflation of the monetary base (yearly) has done nothing to stop this growth and that is impressive. Soon, with the block halving, even the monetary base will grow much more slowly.
Of course the growth of Bitcoin will slow down eventually and it will start to become "just a store of value" and not the super investment it has been thus far, and that's the way it's supposed to be. Something like Bitcoin is not really meant as an investment but it is meant to be good for savings and to work as a store of value. In the long term it truly has been a good savings currency already, it's undeniable.I'm a strong supporter of Bitcoin and I have a significant percentage of my own money in Bitcoin right now, but it is misleading to say that Bitcoin is a good unit of account or store of value. It is just too volatile right now to serve those purposes. It is without a doubt, however, the world's greatest medium of exchange.
Let's take for example the use case of saving for a house that I want to buy in a year's time. If I were to have bought Bitcoins as a 'store of value' or for savings back in June of last year, I would have lost over half of my savings for buying a house. That's just unacceptable for a 'store of value'. Unless, however, the local currency you are using is even worse. That seems like it could be the case for Argentina. It certainly seems to be the case for a country like Zimbabwe.
Bitcoin is a great medium of exchange, and in my opinion, an awesome speculative investment, but store of value it is not. I cannot in good faith recommend people use Bitcoin as a means of acquiring a 'savings account'.
Bitcoin will slow down, but at what price and at what market cap? Will it slow down at a price of $100? A price of $500? A price of $50,000? Maybe governments across the world will launch a coordinated attack on Bitcoin exchanges, shutting them down. Then the price of Bitcoin could plummet to less than $1. There is a huge range of possibility there. As I have said elsewhere, speculators will be trying to find out what the 'true value' of Bitcoin is. Those speculators' sentiments will fluctuate wildly as news comes out about Bitcoin, or for a million other reasons. We have already seen this happen. There will continue to be panic buying and selling, causing wild price swings. That's not a 'store of value', that's a speculative investment.