The rules (with thanks to Dave Barry)

OK, so I went to a concert with open seating at the Kennedy Center last night (Last Train Home at the Millennium Stage)and the circumstances brought to mind this classic Dave Barry column:

You Know Who You Are

Particularly rule number 6:
6. At a movie theater, you may save seats for a few people if the theater is not crowded. If the theater is crowded, you may save seats only if the people you're saving them for are on the premises, defined as ''in the building or the parking lot.'' If the previews of coming attractions have started, and the theater is filling up, and you're still defending seats for theoretical people who have not yet arrived, and an actual person attempts to sit down, and you hiss ''That's saved,'' and the person ''accidentally'' trips and spills that stanky movie-theater nacho cheese all over your hair, and you press assault charges, and we get selected to serve on the jury, we're voting for acquittal.

and rule number 8:
8. At class plays, music recitals, graduations, etc., you may save a few seats for your IMMEDIATE FAMILY, and then only for a reasonable time. You may not arrive an hour early and squat at the end of a row, or even two rows, and save large blocs of seats for relatives so distant that some of them are not even vertebrates.

NOTE: This rule applies even if you have turned the seating area into an indoor yard sale by marking each ''saved'' seat with a personal item such as a sweater, purse, sock, brassiere, etc.

EXCEPTION: If we see a seat marked by dentures, we're sitting somewhere else.

One would think such rules wouldn't need to be stated at a hoity toity venue such as the Kennedy Center. Alas, rudeness crosses all socio-economic categories.