The poster was referring to situations where there is plenty of other space available, and someone plops down RIGHT beside you or DIRECTLY in front of you. It doesn't make any sense, in that situation.
Frankly, it bothers me too (just slightly) in this situation. But I'll either just deal with it, if not, I can get up and move to another location, since there is plenty of beach area and open tables available.
That poster mentioned people encroaching on her personal space. I was pointing out that the only personal space you get in a public venue is the space you take up. It has nothing to do with how crowded a place is.
The beach is different than a place with designated seats, but there are reasons that people do it, and its not to be rude. The beaches we frequent have designated swimming areas, and most people with younger kids pack in like sardines to be able to be in that area so they can see their kids in the water.






