Concerns are mounting over Bitcoin's reliance on the Proof-of-Work (PoW) consensus mechanism. Analyst Anthony Sassano has highlighted the potential risks associated with Bitcoin's security, particularly the possibility of a 51% attack. The energy consumption of Bitcoin's PoW system is also a growing issue, especially in comparison to Ethereum, which has transitioned to a more energy-efficient Proof-of-Stake (PoS) mechanism. Sassano describes Bitcoin's security as a 'ticking time bomb' due to its lack of a sustainable security budget. Additionally, Bitcoin's physical limitations hinder its ability to operate at the speed and scale of current payment and clearing systems.