The once-largest Bitcoin mining pool, Poolin, announced bankruptcy this week. Its founder, Pan Zhibiao, along with two other partners, all hail from Bitmain. Back in its 2019 peak, Poolin controlled up to 20% of the network's hash rate. However, they weren’t satisfied with just earning mining pool fees and started expanding into wallet services and financial lending. In 2022, with China cracking down on mining and the bear market hitting hard, Poolin faced a severe liquidity crisis due to its previous leveraged financing for expansion. The company suddenly suspended wallet withdrawals, forcibly converting users' balances into IOU tokens (I Owe You), essentially issuing debt notes totaling $160 million. To this day, the debt remains unpaid.