I read alot about chair hogs here .... but I can honestly say we've never had a problem.
However, we don't really lie out in the sun. We'll use one chair, maybe two, and put all of our towels and stuff on them, and we are mostly in the pools. I see alot of families take out one chair per person, and they never use all of the chairs. They could easily share, like we do, making more chairs availabile for others.
If we can't find a chair (I can't say that has ever been an issue) ... we'll probably just find a place to keep our stuff. I know on some ships, we have had to go up a deck to find a chair, but a chair is always available somewhere.