This guy doesn't seem to get what bitcoin is or it's purpose. As far as I'm concerned, bitcoin will just be another alternative currency forever. It will likely never replace fiat, and that's fine. It's awesome for international trade, fast transfer, low-fee, and a safe way to store your money (if you're okay with the value of btc fluctuating wildly; if it ever settles then it will be "safe").
I disagree with all of his points. His carbon footprint/malware/Gresham's law points can all be countered with "incentive to mine leaves as the reward goes down, difficulty goes up, and total remaining coins decreases" which means less people will mine. For hideous markets and tax evasion, yeah, you can do both of those with fiat too. It's not a concept exclusive to bitcoins.
Bitcoin is a fiat currency, in several senses of the term. A Bitcoin has no intrinsic value, it is unbacked and its value is not defined in reference to any other asset or quantity.
Fiat currency does not have to be issued by a government, and does not have to be legal tender. And Bitcoin certainly meets one of the "various" definitions given in the Wikipedia article. There are plenty of other definitions of the term it meets -- at root, a fiat currency is simply a currency whose value exists because someone said so, rather than because it's tied to something else. And... well, Bitcoin has value because people say it does, not because it's tied to something else.
I'd argue that all currencies are by some definition "fiat," in that no currency has ever had nor ever will have an objective value. A dollar -- or a bitcoin or a gold nugget -- is worth what we believe it is, and in every case that belief requires some level of trust, usually in one or more institutions. Believing in the Federal Reserve or the US Government isn't intrinsically more (or less) silly than believing in private banks issuing certificates that they assure us are redeemable for fixed amounts of gold, or for that matter believing that the gold itself is valuable. (There's no reason gold is a better backing for currency than silver, shells, or salt -- all of which have been used as legal tender.) Bitcoin's novelty is in attempting to take institutions out of the equation, but it ultimately hasn't taken away the requirement of trust -- and its wild volatility at least raises questions about whether institutions trying to actively manage the value of currency are actually such horrible things.
best case scenario: the future of bitcoin is a technological oddity (curious detail) wherein 99% of people only hold it for the briefest of moments when they transfer their fiat currency from point A to point B. And the people that do hold it will almost certainly be doing so to better exploit fluctuations between currencies.
I disagree with all of his points. His carbon footprint/malware/Gresham's law points can all be countered with "incentive to mine leaves as the reward goes down, difficulty goes up, and total remaining coins decreases" which means less people will mine. For hideous markets and tax evasion, yeah, you can do both of those with fiat too. It's not a concept exclusive to bitcoins.