2. Security
3. Price Manipulation
4. Regulation
¿Another?
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To be honest with you, all of these can become a problem anytime soon. Volatility because you don't know when you will need money and there is also a chance that your coins are really low when you need money the most. Security because you can get hacked anytime. Even you have ledger it can still be stolen by anyone from you. Price manipulation is also like volatility but this time it is controlled by whales. Regulation because any government agency can ban or limit the use of cryptocurrency.