Rare? Yes. It seems that flash mobs are 'a Philly thing.'

WILDING teens are not uncommon.

Newspapers nationally abound with stories of teens - whether in pairs or huge crowds - whose innocent meet-ups devolve into boredom-fueled destructive behavior.

But the idea of teens mobilizing through social media to form marauding mobs intent on vandalism, assault and other criminal mischief?

That might be just a Philadelphia phenomenon, according to one youth-violence watcher.

"I haven't heard of it anywhere else," said Pamela Riley, executive director of the Raleigh, N.C.-based Students Against Violence Everywhere.

Riley's group, a student-initiated program that promotes nonviolence, has more than 1,800 chapters in schools nationwide (although not Philadelphia public schools).

She said that online innovations and mobile media are largely greeted as positive progress, but such technology has tripped up some teens who use them in negative ways.

"We've seen that with texting, with teens sexting; with kids who record assaults and post the videos on YouTube; and now with these violent flash mobs" organized through Facebook, Twitter and such media, Riley said.

"We have to make teens understand, in some way, that these actions have consequences that will follow them through life," Riley added.

Riley recommends empowering youth to become leaders who can exert positive peer pressure.

"We can't sanitize our society and we can't insulate our kids from the world, but we can build young people who can make appropriate and wise decisions," she said. "We do that through education and example.

"Empathy is a protective factor we have got to instill in our youth at a very young age," she added.

Last weekend's flash mob on South Street had ironic timing: This week is National Youth Violence Prevention Week, Riley said.