I had wanted to ask about this situation, though bear in mind I have it third-hand from my mother (who actually bought the ticket) regarding my brother's experience back in December:

He had a paid F ticket SEA - ATL - RSW, and was told by the GA @ SEA, "Sorry, we're overbooked. Go home - you're not flying tonight." He stood his ground, and they "found" him a coach seat (SEA-ATL) , and issued a voucher for a coach-to-first upgrade. He knows nothing about these things, and is not interested in anything to do with frequent flyer stuff (I am interested enough for both of us!). My mom and I were shocked that there wasn't someone either upgraded or on an award ticket (even if they were Diamonds) who wouldn't have been "downgraded" ahead of tossing a (non-status) passenger on a $$$ F ticket.

I'm assuming that the upgrade voucher will only work on an underlying YBM fare (big whoop!), and my mom/brother will either have to go to the airport or pay a phone fee to book it? Also, would it be good for a connecting flight's segments or limited strictly to only one?

Your thoughts on what likely happened that night?

Thanks!