It is funny that you focused on this, but it was the biggest thing that we were upset about on the cruise too! We thought about being jerks and picking up a bunch of books and stacking them in the corner so that others could use the chairs. But alas, I am not a jerk and so couldn't do it. But it did upset us even more that no one on board would remedy the situation. I know that on Radisson cruises we have been on before, the staff cleared the chairs after 30 min of vacancy and I for one appreciated that. On the Oceania cruise, there were some chairs that were vacant, but "reserved" for over 4 hours!