Update: Jan 4. 2013
The Washington Post has a story by Peter Hermann, Jan. 2, "Lanier steps up use of power to close D.C. bars; Businesses suspended 15 times in 2012; Opinions split on cheif's use of emergency order", link here. Police say that altercations outside bars have often started inside them.
It's important to remember that open businesses on a city street generally make it safer for pedestrians, as ordinary street crime will be less on streets that have a lot of normal foot traffic. Most street crime in cities takes place on residential streets away from businesses that are open at night. In Washington DC, there are more police cars near bars just to catch people walking to cars under the influence. Closing bars because of problems near their premises may not make sense for public safety in the long run.