• Crypto-currencies are a new asset that is achieving some notoriety in the capital market. Since its appearance in 2009, more than 10,000 crypto-currencies have been created in the world and more are born every day. Now, most of these “currencies” are empty assets and, therefore, subprime.
• The cost of electricity could make crypto-currency mining unfeasible.
• The system can only process 7 operations per second
• The quantum risk
• 95% of Bitcoins are in the hands of 2.4% of addresses (holders).

You can find the paper here: the English version and the Spanish version