FLASH mobs are strangers meeting to do something whimsical in public. Mobs that beat people up and steal their things are ORDINARY mobs.

I'm not why the two got conflated some time two years back, but it's weird how it has persisted.

@Commentary Colin Because a flash mob is organized, an "ordinary" mob just happens (anger has something to do with it most of the time). I guess the kids in Philly are less inclined toward Michael Jackson choreography, more toward thuggery. But isn't it great that they've learned to optimize technology?