Do seats on excursion buses count? On a Med cruise it was a two hour bus ride into Rome, even before we left the dock there were arguments over "saved" seats. For crying out loud, we all went to the bus together, why couldn't the couples just board at the same time and sit next to each other? Worse, we exited the bus, toured and when we reboarded there were more fights about "savings seats" because some people left a book/sweater on their original seats and others felt reboarding meant they should be allowed to reselect seats. OMG, it almost became physical. I don't recall that kind of behavior on school buses when I was growing up.
Also, the people who leave books/towels/sunglasses on lounges for hours or in some cases (when it is only a towel) are never seen again.
Saving one seat in a theatre is acceptable because the other person may be at the bar or using the facilities but any more than one is unacceptable. If your group can't get there together and on time, sit in the crappy seats.