This is where he lost me. "Market cap" is a meaningless number for cryptos, as it's not realisable at all. It also gets people thinking of cryptos like companies, where you could actually realise something like it.
His entire thesis is "you can't prove this isn't just a bubble of timing!" and it's not a strong argument. Every bubble ever has had people claiming this one is unique.
Crypto "market cap" doesn't work like that - cryptos, including Bitcoin, are so thinly traded that the price is exquisitely sensitive to trades many magnitudes smaller than the total number of units. There's 15 million bitcoins, but trades on the order of 100 BTC can cause flash crashes. e.g. http://www.coindesk.com/high-seas-bitcoin-trading-whales-sti... Apple has 5 billion shares outstanding, but you couldn't flash-crash it selling 20,000 of them - the volume is ~20m/day.
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Investopedia: Thin market http://www.investopedia.com/terms/t/thinmarket.asp
A market with a low number of buyers and sellers. Since few transactions take place in a thin market, prices are often more volatile and assets are less liquid. The low number of bids and asks will also typically result in a larger spread between the two quotes.
Also known as a "narrow market".
A thin market has high price volatility and low liquidity. If supply or demand changes abruptly, resulting in more buyers than sellers or vice versa, there will typically be a material impact on prices. Since few bids and asks are quoted, potential buyers and sellers may find it difficult to transact in a thin market.
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Applied to Bitcoin: if the market is thin, i.e. the order books aren't very deep, then a small amount of trades will strongly affect the price.
So it's not a matter of what proportion of the total units a given trade is - but more of how busy trading is, and how likely a given trade is to strongly affect the price. In Bitcoin, single trades on the order of 100BTC can send the price up or down $30.
(Note also that the quoted "price" is a weighted average of exchanges. The price has been observed going up or down when the blockchain was actually getting flooded with transaction spam, and non-spam transactions were near-impossible; this is because trading inside the exchanges didn't stop, even though it wasn't linked at all and you couldn't transmit bitcoins between them. So the number to worry about is not depth of all order books, but depth of the order book on each exchange.)