I got a $400 travel voucher for giving up a seat on an overbooked flight.
The first time I tried to use it I found out that I had to call to make a reservation and then mail the voucher in and then wait for the tickets to arrive by mail (you cannot do it online). Of course, the vopucher is the only proof you have that you have a voucher - and you are asked to mail it in.
Of course I heard nothing for months, but to their credit when I called to follow up they did have the reservation, did process it and sent my tickets along with the remaining balance on my voucher.
Now - I tried to use the balance of the voucher towards a flight. I paid the additional cost on a credit card and mailied in the voucher. Once again, I have heard nothing. I am sure this is just the way the airlines do business - trying to make as difficult as possible for you to collect on what they have given to you.