I wrote before both, about the general problem of concentration risk and the specific problem of this risk (more accurately, the concentration-implied VUCA environment) in the specific asset classes and the economy. Here is another reminder of how the build up of concentration risks in the financial markets is contaminating all asset classes, including the off-the-wall crypto currencies: https://thenextweb.com/hardfork/2018/09/18/cryptocurrency-bitcoin-blockchain-wallet/.
The added feature of this concentration risk is extreme (87%) illiquidity of major Bitcoin holdings. This means that under the common 'Mine and Hold' strategy, already monopolized, highly concentrated mining pools literally create a massive risk buildup in the Bitcoin trading systems: with 87% of wallets not trading for months, we have a system of asset pricing and transactions that effectively provides zero price discovery and will not be able to handle any spike in supply, should these accounts start selling. Worse, the system is tightly coupled, as Bitcoin holdings are frequently used to capitalize other leveraged crypto currencies undertakings, such as investment funds and ICOs.
The extent of latent instability in the crypto markets is currently equivalent to a Chernobyl reactor on the cusp of the human error.