I once dated a girl who said her ex was a cocaine dealer in the Mission. Born and raised in the neighborhood, him and his crew would have constant scuffles with other small 'gangs' over drug territory. Once he was stabbed multiple times during an altercation over which crew had rights to sell coke at Beauty Bar. She told me this while we were sitting in Dolores and she saw him and his crew smoking weed and drinking in the sun.

Edit: Looking at the map it's kind of interesting that Beauty Bar is on 19th street, which according to this map is on the boundary of three gang territories. I've always felt that the mission is a still sketchy place.