BTC being valued at $16k doesn't make it a good currency, but it's sure a great pump and dump instrument.
@Elizafox deflation inhibits the very definition of currency, but on the other hand, to serve a global economy it needs a market cap in the trillions. It's important to keep this in mind when estimating how much it "should be" worth. People are complaining more now that it's pushing $20k than when it was pushing $2k,but the decimal is placed fairly arbitrarily.
@rook It's important to consider what that capitalisation is coming from, though. If it's coming from speculation, it's not useful as a currency — it's simply a bubble, because payments made in the currency do not have guaranteed consistent value.
A lot of companies don't accept bitcoin because it's impossible to determine refund value.
@Elizafox no argument there, but I think speculation only counts for a few of the orders of magnitude we're seeing. I bet we'd be seeing a very different picture if the original decimal was placed much farther to the left, with correspondingly larger mining rewards, or more frequent ones.
@Elizafox you seem to be overlooking the black market uses that predated the vast majority of speculation. Not saying the black market is good, but it proved bitcoin's utility as a currency up to about two orders of magnitude since dollar parity, or 5 orders since the first markets showed up early on.
Either way, we're only about 2 orders of magnitude beyond that. So it's really not that bad in absolute terms.
Volatility is a problem though, but not an inherent one.