I suspect some readers will say that Assefa Senbet is to blame for screwing up one of his final payments to Citibank on a deferred interest loan agreement. They’ll be right–it was his responsibility. But he didn’t skip a payment, and he wasn’t late. In fact, he frequently overpaid in order to pay it off early. Near the end of the loan, however, he sent in a check for $70 instead of $81. As a consequence, he’s now paying off $887 in deferred interest fees at a 30% interest rate.