Bitcoin is energetically wasteful.
Most exchanges and all exchanges that deal with sovereign currencies are centralized and it beats Bitcoin's purpose.
It is very difficult and dangerous to own and transact with the difficulty of Bitcoin wallets and their risks.
Its fees which had already been unfairly high were recently lowered, but may return to their peaks and surpass them.
Bitcoin forks every once in a while, and each fork eats at its mining pools and user base.
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From @fersher