A term originally associated with fun has turned more menacing.
In popular culture, flash mob has also come to be associated with a large outpouring of violence, such as those that have plagued the United Kingdom this week.
The March 27 shooting in Coolidge Park here was attributed to a flash mob gone awry, according to Times Free Press archives.
"[Flash mobs] started as a fun thing, but it's getting ugly," Mayor Ron Littlefield told the paper.
Chattanooga dance instructor Lindsay Fussell said when she planned an artistic flash mob event in front of the Tennessee Aquarium, she had to be careful to refer to it as a "spontaneous dance."
In some quarters, flash mobs have come to stand for group violence and/or robberies coordinated using social networks such as Facebook and Twitter.
And cities and businesses are reacting. Philadelphia Mayor Michael Nutter announced he plans to combat flash mobs by instilling a 9 p.m. curfew for anyone under 18, according to national reports.
The National Retail Federation issued an 11-page set of guidelines for retail employees to deal with flash-mob incidences, labeled "multiple offender" crimes.
According to the report, of more than 100 retailers surveyed in July, "over three-quarters (79 percent) of retailers report being a victim of a multiple-offender crime in the past 12 months, some of these incidents (10 percent) involving flash-mob tactics."
Picture a day, an ordinary day. Maybe it's a summer weekend, and families are strolling in the sun.
Suddenly, out of nowhere, there's music. Someone begins to dance. Another person joins in. Then a whole group of people, all in sync, begins to move together. A crowd gathers. Onlookers are caught up in the spirit and run to join the celebration.
This is a flash mob, a seemingly spontaneous, but actually carefully planned, outpouring of dance, song or other exuberant activity.
Joyce Teal, of Hixson, has participated in several local flash mobs.
"If you ever want to be pointed at or have people look at you and smile, or laugh, this is a wonderful opportunity to have that happen," she said. "Once the dancing starts and the music kicks in, people start tapping on the shoulders of the people next to them and saying 'Look, look!'"
On April 2, Teal took part in a flash mob outside Loose Cannon Gallery as part of Palate 2 Palette, a benefit event for the Faces: The Craniofacial Foundation of America.
When it broke out, she said, "word immediately spread up the street that they were doing a flash-mob dance down at Loose Cannon. And all these people started coming down to see us."
She said she was recording the performance on her camera phone, secretly waiting for her cue, before running out and joining the group of dancers.
The flash mob was coordinated by Chattanooga Theatre Centre dance instructor Lindsay Fussell, who has also organized such performances at Hamilton Place mall in honor of National Dance Day and at the Tennessee Aquarium last Labor Day, an effort that she said involved 144 dancers.
In addition to choreographing steps for a large group of varying ages and skill levels, Fussell was also tasked with coordinating contacts and schedules, no easy feat.
"The most difficult thing is contacting people through email, Facebook, phone calls, back and forth with messages, all of that stuff," she said. Beyond that, she had to carefully choreograph a seemingly spontaneous eruption of dance -- who starts, who joins in when, what steps are executed to what music. All of this planning is required for a few minutes of performance for an audience that may or may not even appreciate the effort.
What makes the hassle worthwhile?
"It really brings smiles to people's faces," Fussell said. Certain people, she said, will know what is about to happen, but "so many people don't know. When we did the first one, at the Aquarium, there were so many folks who said 'we had no idea that this could happen here.' I think it instills a sense of community in providing free, out-of-nowhere entertainment."
Beyond that, however, flash mobs have become, to an extent, good business.
"We watched this phenomenon with growing interest," said Ann Coulter of strategic planning/visioning firm Kennedy, Coulter, Rushing & Watson, who hired Fussell to plan the 2010 event at the Aquarium.
And, wanting to provide a lively, animated welcome to the Scenic City for both guests and residents, they knew the event had to include two things: The Tennessee Aquarium and the Chattanooga Choo Choo.
"It needed to be iconic of Chattanooga," she said.
Indeed, flash mobs have become mainstream. Businesses are utilizing flash mobs for promotion. The movie "Friends With Benefits" featured two flash-mob scenes.
"Obviously, they're becoming more common," Fussell said. "People are going to adopt whatever the latest trend is. If it's cool and hip, people want to do it."
But have flash mobs, which began in 2003 in New York, become trendy to the point of being uncool? New York Magazine recently placed flash mobs at the top of a list of "pop-culture references that need an early retirement."
Still, Fussell said, she thinks flash mobs still have some shelf life before becoming entirely passé.
"These things are neat now, but they're not going to be neat two years from now," Coulter agreed.