It may sound ridiculous but they are becoming violent, they're not so organized as to call them a gang I'd think, not like there's an actually system of ranks or internal cooperation, but they do follow an MOS and they are becoming a problem.
They're big here in the Seattle/SeaTac area, the mall a friend of mine works Loss Prevention at is having vandalism and theft issues attributed to them and just last week the police are watching the mall as well due to an armed robbery committed by 'them'.
I did put them in quotations for a reason though, I'm not sure there is a them, I don't think there's any communication. It's just otherwise common criminals getting a bit more umption due to their face-paint, fitting in and occasionally find like-minded 'juggalos'.