Movie Etiquette: Is It even Considered Anymore?

I went to the movies Saturday night to see The Woman in Black with a friend. After our discussion on movie theatre etiquette, I paid close attention to those around me.
Upon entering the theatre, I noticed others, along with myself, looking for an open row to sit in. We sat at one end of the row, while another two people sat on the other end, leaving four seats open in the middle. Yet another couple came to our row, squeezed by, and sat in the two middle seats, leaving a seat between me and the other group on the far end. Typical personal space issues.
As people filed in, they looked frantically around, looking for an open row where they would not have to make awkward stranger contact. A few groups even walked around the theatre a few times before finally giving in and sitting next to a strange group.
Another etiquette that I don't think we discussed in class was to be on time for your movie. The movie previews were almost done, and a few groups walked in. In my opinion, that really bugs me. I think people should be there at least five minutes before the previews begin, because then, you won't disturb others trying to watch the previews.  So then, the movie began. You would expect the audience to be quiet and respectful, but there were so many people talking and laughing at parts that were inappropriate. Since this was Daniel Radcliffe's first movie after Harry Potter, I heard numerous Harry Potter jokes throughout the movie, which angered me to some extent. Even though this is completely unrelated to etiquette, people should respect an actor's career, and respect that their role they're known for shouldn't be dragged into their newer works. End that rant.
Anyway, so many people were talking about things totally unrelated to the movie, which goes against the usual etiquette of movies. You would EXPECT people to be quiet, but that's not always the case. I don't think that should be really considered as a "rule" of the movies, considering there's always those few people who talk, disregarding everyone else. Another thing I noticed was during the scary parts of the movie. A face or whatever would pop-up on the screen and everyone would jump and scream out loud. Normal, you think right? Not quite. People prolonged their screams and talking a few minutes after the scary part! I'd expect people to scream, laugh at themselves for acting like babies, and then go back to being quiet to continue the movie. That is probably just me, though. Then there is the etiquette of keeping all extraneous noises to a minimum, for example, drinking and eating. The theatre should be quiet, except for laughing, crying, screaming, etc. I hate it when it's silent in a theatre and all you can hear is someone a few rows ahead of you munching like a horse on their popcorn. I think people should at least have the common courtesy of trying to keep their noise level to a minimum.
So that concludes my movie experience. I had never noticed these small things before, so the discussion in C&I really opened my eyes to the little quirks in people's actions in movie theaters.