David Schwartz, former CTO of Ripple, has raised concerns about Bitcoin's decentralization, arguing that its Proof-of-Work (PoW) mechanism may actually centralize control. His comments follow an incident where Foundry USA, the largest Bitcoin mining pool, mined seven consecutive blocks, prompting discussions about mining concentration and network security. Schwartz contends that PoW is a centralizing force that Bitcoin must actively counteract to maintain decentralization. He highlighted the risks of mining concentration, such as selfish mining, where large miners could exploit the system. Schwartz suggested that while changing the mining algorithm could undermine trust in Bitcoin's immutability, leaving it unchanged might overly depend on miner behavior. The debate underscores ongoing concerns about the balance of power within Bitcoin's network.