I posted this just a few days ago about my experience this past Sunday (09/18/11), so just copied it:
Air Tran is also bad about overbooking. Almost every trip they make the announcement that they are overbooked and need someone to fly out on a later flight. This past Sunday I had the last flight out of MCO and they were begging for four people to give up their seats. There was not a single empty seat on that plane. They were offering two round trip fares to anywhere Air Tran flies, a night in a hotel, meal vouchers, and a guarantee to fly out on Monday morning. Two ladies finally accepted, but they continued to make the announcement that they needed two more seats. One guy finally yelled out that any of us would be crazy to accept their offer, since Air Tran would no longer be flying out of DFW after Nov 22nd, so we wouldn't be able to use those air fare vouchers they were offering anyway. The two ladies that had accepted the deal, immediately came back up to the desk, said they didn't realize Air Tran was going to stop flying out of Dallas that soon, and they wanted their seats back. They were not allowed to get them back. Both they and another couple who were bumped were very unhappy when we left. The man was saying that they had paid for their tickets and expected a seat on that plane and just because they hadn't paid for their seats was no reason to bump them and Air Tran had no business overbooking their flights. The agent explained to them that all airlines overbooked their flights, expecting cancellations and no shows and that there simply were not any seats for those four people. Since it was the last flight, they would not be flying out until the next morning.