I heard this happened this morning at DCA prior to a DCA to ATL flight. They were not sure how many volunteers they needed but if you wanted to volunteer, you had to submit a bid in order to get bumped. So basically, they took the lowest bid(s) and gave the passenger(s) Delta vouchers in those amounts for future flights while bumping them to later flights. Usually you'll hear a $300 or $400 voucher being given for a future Delta flight. But has anyone on here heard of those volunteers actually having to submit bids with the hope of being bumped?