Here's another question - something I don't understand. On the upgrade list the night before my flight, or even in the morning when I check at home - I'm frequently in a position to receive the upgrade (e.g. #2 for three seats). But when I reach the airport and check with the GA, I'm now #7 or #23 or whatever. They don't have a good explanation for this - usually indicate that it's because of delayed arrivals or standbys needing to be seated. If it happened just once or twice I'd think nothing of it. But it's happened for many of the segments I've flown this year, and didn't get upgraded. Are there that many DM/PM same-day standby's that are taking the upgrades?

Is there some other explanation?