When an in-the-money stock option expires does the broker always execute it or does its value become worthless if the owner doesn't execute it?
It depends on the broker, each one's rules may vary. Your broker should be able to answer this question for how they handle such a situation. The broker I used would execute and immediately sell the stock if the option was 25 cents in the money at expiration. If they simply executed and news broke over the weekend (option expiration is always on Friday), the client could wake up Monday to a bad margin call, or worse.