New Orleans boasts the best crowd control in the country. Millions of revelers take to the streets during the Gras, and there are hardly any violent or destructive incidents. The department claims that people from around the country visit New Orleans to discover the NOPD's crowd control secrets, but I think I have a general gist of it: the NOPD don't expect anything terrible to happen.
Case in point: when the Phillies made it into the world series this fall, people filtered over to Broad Street, and as I was walking in the crowds I started to feel real happy, reminded of how nice it really is to be in a place, surrounded by people, knowing that they are thinking the same thing you are (in this case, WOO HOO). But when I got to Broad street, there were about 50-70 cops standing in the median, arms crossed, stares cold, eyes narrowed. They looked like some SHIT WAS BOUT TO GO DOWN, and they didn't look happy about it. They were expecting something to happen. Sure enough, about five minutes after I got there some guy shot off a bottle rocket in the middle of the crowd and was pinned to the ground by about four police within two seconds.
NOPD, on the other hand, stick to the outer edges of the crowd during Mardi. They act as the parties' referees, not enforcers. When someone is expecting you to break the rules, you do. Which is why racial profiling is so problematic and circular. It's just another example of your expectations of what is going to happen can radically change what actually happens. And the best part about expectations is that they are in your control!