I am not exactly sure what you are refering to. I once got a $500 voucher from AA because I had to fly the next day out of Las Vegas, NV. That does sound good, doesn't it. Well here is the catch:

The money we got for the Hotel was something like $40 since they wanted to book us in some crappy motel. No sane person is going to wan't to stay in a hotel in Vegas.

But the real bummer came when I tried to redeem the vouchers. Almost all sorts of blackout dates applied. I was going to Hawaii and found a reasonably priced flight online. I then called AA, since this is the only way to redeem the tickets. They immediately found a flight for about $2,500. This means I would still have had to pay much more with the voucher than I had to pay on Orbitz. So after some patient convincing they found me a flight that was still $250 over the price of Orbitz. This was the best they could do (I guess) and after two hours on the phone I gave up.
This meant the $500 vouchers resulted in a savings of about $250.

I would therefore never go on a waiting list for a long-haul flight but I wouldn't mind doing it again for shorter flights. The airline was desperate, since they had overbooked the flight a lot and had to leave the airport or get penalized. All flights were delayed and things were quite chaotic. Normally you would not get such high valued vouchers for short flights (mine was about 90min). I guess for short flights you can expect something like 50%-90% of your ticket price (depending on how desperate they are and how long you have to wait). The flight next day was first class, a nice benefit too.

Andre
Check out my Photos

Airlines always overbook flights. For them to be profitable, they have to operate their planes at full capacity. I think that they perform studies that show the percentage of people that do not show up and overbook by that much. Its simple statistics. They know they have to pay compensation to those who cannot get a seat, but they are also going to waste money if they don't overbook. I think the sweet spot for them is around 5%-10% overbooking.

If you are not bound by tight schedules, you can take advantage of this situation.
If they cannot find enough volunteers, the airline is going to bump passengers. For those who get bumped involuntary, they have to give them a ticket for a later flight and some other compensation (regulated by law).

On the other hand voluntary compensation is negotiable. While most airlines are getting away with $200 compensation, they sometimes have a hard time finding volunteers and compensation can be much higher. It depends on your negotiation skills. So don't be shy, they would do the same to you (try getting a flight on short notice and see what they charge).

Compensation is generally in the form of cash vouchers that have to be applied toward future travel. You don't have to be a frequent flyer with that airline and you don't have to have any miles account with them. Anyone can take advantage of the offer.

The worst that can happen is that you agree to be put on hold. After the plane fills up, they still have some crappy seats. Since you just forfeited your seats, you are required to take what's available. So if you made reservations for good seats, you could loose them. That is why I am hesitant to volunteer on long flights as Andre mentioned.

Now I really feel that I got ripped off. Thanks for your answers.

I have done this a few times and it worked out fine if you have time to stay maybe the Airline company you did this from is different, but we got a free hotel, meals, and a flight next mourning plus tickets but they did have blackout dates.

I have never tried the standby on any airline. I usually take the redeye and try and avoid going to certain areas of the world that is generally their tourist season,

I have also seen the standby/vouchers being discussed via the news. And always wondered myself if they were worth the wait.

I guess from this thread it is a 50/50 chance of it being good or bad.