Back when I was a frequent business traveler, I often took the bump.
Me and three other people did the multiple bump from Detroit to Milwaukee on a Sunday, starting with an 11a flight, and getting 2 or 3 more . . . and still got into Milwaukee by midnight. The total rake per person was $1,100. That was on Northwest back in 1995, and I used my vouchers for a trip to Germany the following spring. The airlines are better at not booking volunteers on "the next flight" which may also be oversold. It has never happened for me since.
A word of caution about checking in online and being asked if you are willing to accept "denied boarding compensation" because your flight is oversold. I did that last summer flying out of Jackson, MS on Delta. They ask how much you are willing to accept, and as long as it is at least no more than what they will initially offer at the gate, they will accept "your price" and you will get the bump. The downside is that if they end up going over your price, that is still all you will receive.
It used to be that if you volunteered at the airport when they offered let's say $300, but they eventually had to go to $500 . . . EVERYONE got the $500. But that doesn't apply with the check-in process and setting your price. In Jackson, I said I'd take the bump for $300, they did get to $500, and I was out of luck. Even worse, the gate agent at Jackson really botched my rebooking process but that is another story for another day.
For the most part, taking the voluntary bump can be very dicey. Because they can tell you one thing at the gate about when they can get you to your final destination, but in the time it takes for them to board the flight and do the paperwork, the rebooking could be delayed enough to cost you the ability to get the new flights you were initially told you'd get. I had one set of flights that had me getting home around 4pm. The rebooking was going to have me in at 8pm, so no worries. But by the time they got to actually rebooking me, that set of flights were gone and that particular airline would not use others to get their passengers tot heir final destination . . . I was stuck until the next morning! NO BUENO!
Last story . . . if an airline KNOWS that their flight in a connecting hub is oversold, they will intentionally delay passengers coming in so that they can deny and not compensate based on the 15 minute boarding rules. It happened to me and a business travel companion, flying from Milwaukee through Memphis and on to Kansas City.
We left Milwaukee EARLY . . . and arrived at Memphis 30 minutes late. With a 45 minute connection and only having to walk down two gates on the same concourse, we walked up to the gate 10 minutes before the posted departure time. They had already buttoned up the flight, door was closed.
When we asked about our connection and the time, the gate agent said the flight was oversold, we were not there 15 minutes before the scheduled departure and our seats were given to the next ticketed passengers w/o assigned seats. Told we would not receive compensation, we were further told the earliest they could get us into KC was like 7pm that evening. (Our original schedule had us there by noon for meetings scheduled to start at 2pm.)
Totally not acceptable but they were unwilling to do ANYthing more to help us out. I ended up figuring out a way to get to Wichita, KS . . . rent a car and get to KC around 5pm . . . including the drive from Wichita to KC. We totally missed that day's meeting, but made the dinner event.
It was a colossal hassle and Delta was useless in trying to help us out. Worse for my travel companion, his luggage was lost in all of the hub-bub and he had to buy clothes for the meeting the next day. He finally got his stuff on the day we were scheduled to depart KC.