But I don't think it means people won't spend it or trade it for some other currency or asset. If you held a bunch of bitcoin while the price in USD doubled, and you happened to want a new smartphone, you're sure you wouldn't buy one?

If you were absolutely confident the price would quickly rise even more, maybe you would prefer holding, but if you really want the phone and you think BTC/USD has some risk?

I think the presence in the market of an asset that many people believe is continually underpriced would have a general effect on spending, not just on the utility of that asset as a medium of exchange...

Only if obtaining BTC is frictionless and fee-free, something far from universal.

Which is kind of crazy and defies all logic - cryptocurrencies can be manufactured without any limit, even Bitcoin can be cloned and rebooted, creating a new currency space/ledger that's fresh.

Fiat currency can also rise and fall 10% in a single day. Problem is that moving the market that much in every day is impossible due to a huge market cap, which BTC does not have.

All cryptocurrencies are not user friendly. Cold, hot wallets, privacy issues, what is the best way to store them, how not to accidentally lose everything etc.

Mass adoption depends a lot on user friendliness which a bunch of cryptographers aren't concentrated on solving.

So, it won't be used as a currency not because of its deflationary nature but because it's just not as convenient as fiat currency.

Scaling issues are also a big blocker. Currently, BTC transaction fees are higher than those imposed by banks. It's no longer a cash, just a store of value.

Core devs are behind a private company, trying to milk the blockchain even more, which will also lead to bitcoin not being used as cash, but they'll sell their own sidechain and offchain solutions, probably just to enterprise.

Blockchain tech is great tech. Cryptocurrencies like Monero are absolutely brilliant. But I'm doubtful of mass adoption, mostly because torrents, free software, as amazing as they are, and convenient for superusers, don't have mass adoption too.

If Bitcoin does get mass adoption and becomes THE worldwide currency then that also means that the volatility will decrease significantly to the point where I wouldn't have any problem transacting using Bitcoin.

I realize the idea of that actually happening is pretty insane and it is probably more likely that the value will go down to zero, but it is hard to predict the future.

When Bitcoin was $100 then a $1 move in price was a 1% change.

When Bitcoin was $1000 then a $1 move in price was a 0.1% change.

If Bitcoin gets mass adoption then the price per Bitcoin could be $50,000 (assume $1 trillion market cap) or higher. At that point a $1 market movement would be a 0.002% change. To get the same 10% movement as at $100 would require a $5,000 market price swing which while possible is less likely.

It means a lot more money would have to be bought or sold to cause the same percent movement in price.

Bitcoin is already much less volatile today than it was in the past.

That a big IF. And with the transaction costs it has, I don't see it getting mass adoption any time soon.