Airlines cannot afford empty seats. That sounds like an obvious statement, but many air travelers fail to understand the lengths to which an airline will go to guarantee all of the seats are filled.
Fact: a number of people with confirmed seats will not show up at the gate. Some are business travelers who buy very expensive tickets allowing the option of a late cancellation at no charge.
The airline bean-counters have determined the compensation for an airline bump is a good investment if it allows continued overbooking of flights as a matter of policy. All of them have overbooking formulas that in theory compensate precisely for the number of travelers apt to be no-shows in a given place and time. As you can imagine, the formulas don't always work well in all situations.
That's why some people think Mondays and Fridays (when there is a lot of business air travel) are good days for an airline bump. The same could be true for busy holiday periods or flights to tourist destinations. There are even websites such as Bumptracker that attempt to give you the best possible guess of flights and times when an airline bump is most likely.
