As a speculative asset BTC is even more risky. BTC transactions are processed through an algorithm referred to as replace-by-fee (RBF) which allows the clearance system (miners) to discriminate transactions based on the fee each transaction is willing to pay. In times of high volatility, when extreme price swings happen, big players can easily prioritise their own transactions at the dispense of retail investors by offering to pay high fees. At some point in December 2017 there were over

2000 transactions with a fee of over $1000