The best time to choose seat assignments?

Q. My wife and I think we're savvy travelers and like to think we know all the tricks of the trade. Lately, we've had a disagreement about when are the optimum times to request a seat assignment and to check in for your flight. She feels that if you wait until arriving at the airport to get a seat assignment, the coach seats might all be assigned and they would likely give you an upgrade. She also feels this is the case for checking in later at the airport.

It seems to me that if all the economy seats are assigned, they would select one of their best customers (a very frequent flyer) for the upgrade and give you that person's economy seat. I'm guessing that checking in at the last minute only increases the chance that you will get bumped. If this is what you prefer, fine. So who's right?

A. I'd say you're right, and your wife is wrong. Airfarewatchdog wonders if all airlines won't do this one day in order to increase revenue. You're right that airlines are more likely to upgrade someone who has attained upper status in their frequent flyer programs. And to answer the bump question, we think it's true that you increase your chances of being bumped if you show up at the airport without a seat assignment. On the same subject, some airlines, most recently British Airways, are charging for advance seat assignments (even in business class).