Even the wikipedia entry for Knuth checks has an image of such a check with the full ABA and account number on the check, with only the most inconsequential data (to a forger) blurred out. It's sad that he had to make the change, but if I was doing something that resulted in the full data for my bank account being available on wikipedia and google image search (let alone thousands of CS cork-boards across the nation), I'd probably put a stop to it too.