I'm wondering if some of these swarms aren't planned, in the sense of being part of the organized stuff. It's more that since next to no ones been arrested for closing down major highways, disrupting holiday activities, even burning and looting, it must be an okay way to express ones emotions. Heck, they've even been called "peaceful protests". Those with thuggish tendencies figure it's okay because (1) police aren't supposed to shoot them whatever they do and (2) notbody's been punished much for outrageous behavior.
I'm wondering how this all works for New Years Eve, when so many localities have major public activities.