What a difference a day makes.On Wednesday night, I posted an update on Occupy Oakland, one of the most active of the various Occupy groups in the country. The group had just organized a very successful General Strike and march on the Port of Oakland. At the end of my post, I alluded to the presence of a small group of violent militants bent on property destruction and conflict with the police. I expressed a hope that they would not re-emerge in force later in the evening.Alas, it was not to be. The militants, who are apparently affiliated with a group known as the black bloc, came out in force Wednesday evening. The spark was the effort by a number of Occupy Oakland demonstrators to occupy a vacant office building. The occupation produced a very strong police response, including the use of beanbag rounds and tear gas. The conflict quickly became a street battle between masked militants and police in riot gear. The militants lit fires in trash cans, threw rocks at the police, and left graffiti on a number of surfaces. In the fracas, yet another military veteran, Kayvan Sabeghi, was seriously injured by the police.I was in downtown Oakland for a business meeting the next day and walked by the intersection of 14th and Broadway, the center of the occupation. The intersection looked awful, with many of the building walls now covered in graffiti. Many windows, particularly those of local bank branches, were boarded up. One story making the rounds today was about longtime Oakland resident and developer Paul Tagami, who pointed a loaded shotgun at militants trying to break into his building. Its sort of the universal dont come any farther sign, he told the Contra Costa Times.Many in the Occupy Oakland movement decried the violence and vandalism and a number have even volunteered their time to wash the graffiti off of buildings or to sweep up broken glass. But that has not protected the broader movement from an enormous public backlash. At a city council meeting last night, Mayor Jean Quan and many members of the City Council spoke in favor of the broad aims of the Occupy movement but raised serious concerns about the impact it was having on the city. While police resources have been concentrated downtown, police response times in the rest of the city have grown dramatically. The cost of police overtime is rising rapidly.The private sector is also being affected. Oakland has never been a destination city like New York or San Francisco. The small businesses in downtown often hang on by their fingernails. Representatives of the Chamber of Commerce who attended last nights council meeting claimed that a potential major downtown office tenant had decided not to come to Oakland because of the continued civic unrest there. My own company has had to shut its downtown offices twice over the last year and I can understand why a business not already committed to Oakland might wonder about the risks of locating here.The events of the last weeknot just here but across the nationsuggest the Occupy movement is at a crossroads. It has succeeded in putting economic inequality and the plight of working class Americans back on the nations political agenda. The success of Wednesdays general strike and march to the port suggests the movement has the potential for broadening beyond its current core of supporters. But if the encampments become an end rather than a means and if the movement cannot restrain the violent within its midst, it may ultimately do more harm than good to the cause for which it is ostensibly fighting.