There's a lot of courtesy in the lines usually. It's all about who you are with though.
When I got a 360 people left for a couple hours at a time and nobody cared.
When I preordered a PS3 a few weeks ago I got there at 2 PM, pitched a tent, then left for a few hours. Then I came back for a couple hours, went back to campus to go to a party, drove back and slept in the car until 8 AM.
So I really only effectively "camped' for 5 or so hours. These guys are probably doing the same thing (if they aren't I feel bad for them).