I agree with those who say that society is heading south when it comes to manners (whoa, I'm sounding old).
Unfortunately, everyone thinks of themselves, and that's it; there is no one else in the world around them. Take driving, for example: "I don't have to pay attention, others will move out of my way."
The biggest problem is that sometimes these people are rewarded with their bad behavior. There is usually no consequences for those that stop in the middle of an auditorium when told to move to the end (I think I see this EVERY time I go to one of these attractions). Teenagers who do not need a wheelchair using it to get ahead are doing so because it gets them ahead. Those that drive in the highway lane that's about to close do so because it saves THEM time.
If you reward a toddler for throwing a temper-tantrum, they're going to use the tactic again. Same thing with people of any age.
Bottomline: I'm not advocating locking these people up or even throwing them out of the park, but there has to be some negative consequences for their rude actions that'll make them have second thoughts before they act that way again. It's the only way things will improve.