I recently received one for an ATL-EWR flight that was delayed due to weather. It was 2 months after the flight so I had to think back to connect it to the past experience. It's funny, I never get compensated or an apology when CO has seriously messed up but I get compensation when I know that weather was obviously the problem and know it was beyond CO's control. I'll never turn down the gesture or the miles but it does seem to be random. Maybe just a good manager somewhere going the extra mile for customer service?