I've never had someone be so brazen as to "borrow" the patio furniture from a unit I was staying in, but I've certainly observed the chaise lounge hogs at resorts we've visited over the years. Maybe it's just luck, but the resorts that are part of the Hyatt system just don't have this problem, at least in my experience. Hyatt is a smaller system than the big guys like Marriott and Hilton, and maybe that is a factor in designing resorts that aren't overcrowded and support facilities that serve their guests comfortably.
Others here have made the observation that people generally have seemed to forget their manners and are more rude than they used to be. If that's true, it may partly be because of the effects of social media. Other threads here on TUG have discussed this in the past, but the extreme lack of civility on social media cannot help but carry over to the way people interact with others in person and not just electronically. When you see no problem in demeaning and degrading someone you don't even know on FB or Twitter, what's the problem with stealing their patio furniture or hogging lounge chairs at the pool? After all, you were there first and it's a dog eat dog world, right?
I appreciate this quote from TV journalist Ted Koppel:
"Aspire to decency. Practice civility toward one another. Admire and emulate ethical behavior wherever you find it. Apply a rigid standard of morality to your lives; and if, periodically, you fail--as you surely will--adjust your lives and not the standards."
There's another way of saying it--one that is ancient but no less relevant. It's called The Golden Rule: Do unto others as you would have them do unto you.