This past weekend I did a quick EWR-SFO--out Sat back Sun, where I was very happily EUA'd both ways. On my return flight Sun am, the flight was pretty empty in back and the FA's made an announcement after takeoff that those in the coach cabin should fell free to move to an empty seat, as there were many available. BUT-- they also said NOT to take any of the exit rows or Premium seats, as those would cost extra dollars ??? When do they sell those seats after takeoff ?? They did not say how much they would cost, but only not to take them. I thought this a bit odd, and as I was seated in 1F, I didn't get to see if she was joking or serious.