I saw that as well, it baffled my mind. I have a hard enough time getting my 11 month old to sleep in a quiet, dark room, never mind in front of a 40 foot movie screen with deafening audio!
When I went to the midnight show of Spiderman, there was a baby 2 rows in front of me. I sure wouldn't have done that for fear of waking the kid. But the baby slept through the whole thing.