I was talking to a co-worker today about movies, and movie theaters. One that I recommended, she had never been to, and asked, "Is it clean?" Clean for a movie theater, I guess. Then, the thought occurred midway through that I never understood the way people leave their trash on the floor at the movies. They take in a bag of popcorn and some over-priced beverage, finish it during the film and then leave the trash on the floor for a kid with a plastic bag to pick up when the movie is over. I never figured out how that became the custom, and immediately reasoned that it's because the theater is dark and they can leave junk without anyone knowing exactly who left it. Then I realized that people do the same thing at baseball games. After the game, the stands are literally littered with trash, presumably for some stadium employee to pick up after the fans are gone. Mostly, it's brightly lit, so the darkness argument doesn't stand. That leaves me with the sam...