I thought I'd post about a recent experience, and I may try to do this more in the future.

I was using a free United ticket from a time when I got bumped. I was on my return leg, which was BNA to PIT, changing planes at ORD.

My return flight was oversold and they asked for volunteers. I gave up my seat, and since it was the last flight of the day, and all of the other airlines were completely full as well, they were going to have to book me the following day. I asked that they put me on the direct USAirways flight, which they did.

Lo and behold, on my most recent statement I see that I was credited miles for this flight, which would not have happened on UA since it was a free ticket! And since it was apparently considered a full fare ticket, I got 750 miles instead of the 500! And of course I got another free ticket because I was bumpled!

This was a good day to (not) fly!

I will have to try this again in the future--zero cents/mile.