Banks are keeping closer tabs on your reputation than ever before — and it may explain why one Sapph

Over the past year, stories have piled up in online communities of credit-card super users suddenly having their accounts shut down by JPMorgan Chase. The case of Bryan Sequeira seemed similar at first, but upon closer inspection, it proved particularly unusual and confounding. Sequeira, who has a strong credit profile and doesn't game the points system to maximize rewards, was informed this summer that his accounts would be terminated by Chase. But even after his appeal, the company not...