How a student’s surefire bet on Polymarket went to zero—thanks to fine print

A 20-year-old student at Kings College London lost $35,000 after Polymarket changed the rules of a bet he had placed. Hunter Guo had purchased thousands of contracts predicting that Strategy, a bitcoin-hoarding company, would disclose selling bitcoin by May 31. When Strategy announced its sale on June 1, Guo believed his bet would pay off—but Polymarket later clarified that the disclosure had to occur by 11:59 p.m. ET on May 31 to count. The value of his contracts dropped to zero within seconds. The incident highlights a controversial practice in prediction markets: issuing clarifications to existing bets. Polymarket’s move sparked criticism from crypto firms like Galaxy Digital and Arca, which called the decision a ‘debacle’ and illogical. Todd R. Snyder, a former New York state gaming commissioner, argued that such rule changes undermine trust, turning markets into ‘rigged casinos.’ Prediction markets rely on user confidence to function, but disputes over contract terms erode credibility. Polymarket and its rival Kalshi have faced similar backlash for retroactive clarifications, such as Kalshi’s decision in April to invalidate bets on Venezuela’s leadership unless Nicolás Maduro was confirmed as the winner by a set deadline. Guo, who had hoped to buy a Porsche with his winnings, said he cried for two days over the loss. The case reflects broader concerns about transparency in the fast-growing, loosely regulated prediction market industry, where platforms often struggle to align real-world events with binary yes-or-no betting structures. Polymarket, which partners with Dow Jones, has been expanding its offerings with hundreds of new contracts monthly. However, critics argue that rushed expansions lead to ambiguous bets and controversial resolutions, damaging user trust. The platform defended its decision, stating clarifications ensure contracts align with their intended meaning, but the Strategy bet remains a high-profile example of how fine print changes can derail financial outcomes.