>>>>>edit: actually, I've never seen one

I've hardly ever seen them either, but the two times I have are:

1) A couple spring break Fridays out of MSN. BIG song and dance at the gate, followed by song and dance onboard the aircraft shortly before closing. One time it worked, and they got a last-second volunteer (the singing and dancing was particularly fun). The other time the NWA gate agents were terrible - - they had no concept, didn't get any last-minute vols, and then over the intercom called off the plane (!) the last person to officially check-in - - a college student, who then left the plane sobbing - - I was watching from 1A, but had to make an international connection or I would easily have offered.

2) Change of equipment in MSN. The substitute DC-9-30 was a lot tighter than the originally scheduled DC-9-50, and wound up yielding 14 oversells. I volunteered, as did a whole raft of others, but three pax were still involuntarily denied boarding. They were kind of miffed, but then took the $300 NWA travel voucher as compensation, without knowing that they could have gotten a better deal in pure cash if they had demanded their rights. I would have said something, but I didn't want to make any enemies among the dear agents at my home airport.