No offense... I just watched the video. the video didn't show much except for the cop telling everyone to leave. People didn't comply and on top of that, people were cursing at the police. fuck this fuck that will not go over very well with them and especially when they know drinking is going on. as soon as he started to arrest the one guy, you made a crowd around the cop, and even someone was holding a guy back.
Now if you had left... they probably would have got you for a public intoxication...
Another thing:
http://www.google.com/search?q=linco...ient=firefox-a
first link for me is about Lincoln cracking down on underage drinking, their "party patrol", it even goes into plain clothes officers go to parties and bust for underage drinking or selling cups to get into them.
So obviously it doesn't have to be a felony as you said for the police to come in.