Flash mobs are becoming an increasingly terrifying phenomenon in many American cities. Generally organized through technological means -- either on social media networks like Facebook and Twitter, or through text message or email -- flash mobs see groups of people instantly gather in a specific location, often for sinister reasons.

There have been flash mobs in Washington D.C., Pennsylvania, Ohio, Illinois, Wisconsin and Iowa. These U.S. gatherings are generally malevolent, and in recent months gangs of kids have attacked innocent people in the street, robbed stores and damaged property.

But flash mobs aren't new, nor are they unique to the United States. While some flash mobs are meant to be fun, like dances in malls, people moving in slow motion inside a Home Depot, or 3,000 people suddenly freezing on the streets of Paris, this list does not address those kinds of events. Instead, it looks at the sudden demonstrations that shatter a public image, challenge the social order or overthrow governments.

Generally, the biggest flash mobs are demonstrations of public will, not of public violence, but there are always exceptions to the rule. Here is the list of the five most important flash mobs to date.

- 2005 Cronulla Riots in Sydney, Australia -

In December 2005, 5,000 people gathered in the Sydney suburb of Cronulla to protest recent attack on Australian lifeguards by a group of Lebanese men. The event was in part coordinated through text message, but after a number of people who appeared Middle Eastern were attacked and beaten by the crowd, police prosecuted a group of Australians for inciting violence through inflammatory SMS messages.

Every f------ aussie. Go to Cronulla Beach Sunday for some Leb and wog bashing Aussie Pride ok,” one of the messages read.

“Just a reminder that Cronulla’s 1st wog bashing day is still on this Sunday. Chinks bashing day is on the 27th and the Jews are booked for early January,” another read.

- Tahrir Square, Egypt -

On January 25, more than 50,000 people flocked to Tahrir Square in Cairo, many of whom were informed of the gathering via Twitter, Facebook and other outlets. A Facebook page called Tahrir Square was even maintained throughout the revolution, which reported on the events in the square as well as encouraged others to join the protest.

The Egyptian uprising may have started as an exercise in the power of social media, but it didn't end that way. Six days following the initial rally, wireless internet was shut off, yet the protests in Tahrir Square grew larger, reaching anywhere from 300,000 to one million people, according to reports.

However, with Mubarak now in prison and the country trying to figure out its future, activists are again taking to Facebook. They are uploading photos and stories from both pre- and post-revolution Egypt, and finding that social networks are an effective tool of communication.

- Green Revolution: 2009 Iranian Election Protests -

Sometimes called the Twitter Revolution, thousands of people gathered in cities in Iran in defiance of President Mahmoud Ahmadinejad. Ahmadinejad won his re-election in a vote that was widely considered to be fraudulent. Protestors used Twitter, as well as other social-networking sites, to communicate with each other, and with the Iranian diaspora around the world.

Ahmadinejad's government temporarily shut down the internet, as well as blocked sites like Facebook, YouTube and certain media outlets, but young Iranians tweeted lists of Web proxy servers, helping one another get by the restrictions.

- 2001 EDSA Revolution in the Philippines-

President Joseph Estrada was overthrown in the Second People Power Revolution, when around one million people gathered in Manila. Communicating through texts, Filipinos gathered at a monument commemorating the peaceful removal of President Ferdinand Marcos in 1989, where they staged a massive, four day rally against government corruption. It was the first time text messaging was used in such a way.

Estrada was peacefully removed from power. While some criticized the event as a dent on Philippine democracy, others hailed it as a popular uprising executed without the use of weapons or violence. Cell phones were key in the organization of the demonstrations, and the protest grew quickly due to mass communication between city residents.

The rapid assembly of the anti-Estrada crowd was a hallmark of early smart mob technology, and the millions of text messages exchanged by the demonstrators in 2001 was, by all accounts, a key to the crowd's esprit de corps, Howard Rheingold wrote in his book Smart Mobs: the Next Social Revolution.

- 2011 London Riots -

This month's riots in the United Kingdom were sparked by the same communication methods that were employed in Iran in 2009. The riots started when a sudden, organized march materialized in Tottenham in North London. But when mounted police got involved, both sides panicked, setting off looting, arson and general mayhem.

Thanks mostly to BBM, the BlackBerry instant messaging service, youth all over the country began amassing in commercial centers, breaking into stores and destroying everything in their path. For the first three days, destruction and chaos ruled over police and order. People set fire to cars, buses and buildings, and groups of masked kids robbed people in restaurants and on the street. Five people were killed over five days, in incidents that have been deemed murder.

It's easy to credit (or blame, depending on the side one supports) technology for the demonstrations, but social media is only a tool, and not a cause. While flash mobs, in their current iteration, may not have existed in a pre-texting era, there have always been uprisings, as well as gangs, civic unrest and unexplained brutality.

Some politicians -- including some in the United States, like the Cleveland city council, which voted unanimously to ban the use social media or cell phones to start a flash mob -- believe that banning the use of social networks to organize demonstrations will stop future demonstrations, but that is a naive and dangerous assumption. Not only does criminalizing technology not get to the root of the problem, it will do little to deter youths. More importantly, restricting the rights of citizens will only make them more likely to lash out, as was evident in Egypt and Iran.

As the ease of communication increases and as networking platforms become more widespread, the flash mob trend will get more intense before it begins to lessen. This trend will eventually be curbed, but fighting the technology is not the means to an end.