If you google “teenage rebellion,” you get a gazillion sites that explain how to cope with, prevent or quash it. You even get advice about how to medicate it—a couple of years ago, bloggers began talking about “oppositional defiant disorder,” though most of the response to that diagnosis was highly critical.

What seems to have gotten lost along the way is that youthful rebellions can have tremendous creative power. Young people behaving in ways that are counter to the status quo have shaped society and popular culture. Before we dismiss all rebellions as phases or growing pains, and all young independent thinkers as Holden Caulfields or James Deans, it’s worth considering the transformative force of youth-led movements.

Teenagers and 20-somethings who defied expectations and challenged conventional wisdom about what can and can’t (or shouldn’t) be done have changed the world. Take Woodstock, an event that’s now looked back on nostalgically for its innocent celebration of peace and music. The average age of its organizers was 24, and the average age of festivalgoers has been reported to be about 22—a number that undoubtedly reflects a large group of teenagers.

The nation was bitterly divided at the time, yet the festival brought together more than 400,000 people from around the country. Impressive as the roster of performers was, people who went—or wish they’d went—look back most fondly on the spirit of generosity and collaboration that prevailed. As New York Times columnist and Woodstock attendee Gail Collins has pointed out:

The Woodstock festival (“Three Days of Peace and Music”) has been celebrated for 40 years as a great moment in American cultural history, although we’ve never quite agreed about why. Sometimes the argument seems to be that it was important because nothing terrible happened.…

“Nobody killed anybody, nobody raped anybody, nobody shot anybody. In the history of humankind, I think it’s probably the only group of people that size that didn’t do any of that,” said David Crosby of Crosby, Stills and Nash.

And yet, at the time, even as concertgoers “treated one another very kindly under extreme circumstances,” wrote Collins, their parents worried about them and presumed the worst. Now kids can go to festivals without all the hand-wringing. Large, peaceful gatherings are far less noteworthy, thanks to a group of young people who didn’t let precedent deter them.

In the 1980s, teen rebellion looked like the suburban misfits in John Hughes movies: Detention became almost fun in The Breakfast Club, and Ferris Bueller gleefully took the day off, reminding us that “life moves pretty fast. If you don’t stop and look around once in a while, you could miss it.” Hughes created entertainment, to be sure, but his portraits of rebellion as witty and wry became touchstones for a generation of Americans.

In the ’90s, Kurt Cobain gave voice to a less idealistic version of youthful rebellion. In his early 20s when “Smells Like Teen Spirit” took off, the Nirvana singer crystallized the disaffection of teenagers in a recession. Although he was uncomfortable with the “spokesman of a generation” label, that’s what he was—and he reinvented the music business. NPR.org explained:

Nirvana was part of a movement that believed anyone could produce music. Neither money nor connections nor even talent were prerequisites. But for all the band’s anti-corporate rock credentials, Nirvana’s legacy would have a very corporate impact on alternative rock. With its success, record companies turned grunge into one of the most profitable and best-selling rock sub-genres. Years later, the acts that dominate the charts pose as anti-rock stars—and, at the same time, make a lot of money doing it.

A decade later, one of the most apparent forms of teenage rebellion was hacking. Last year, an 18-year-old hijacked the Twitter accounts of President-Elect Barack Obama, Britney Spears and Fox News. In 2005, a 20-year-old successfully launched bot attacks on a Department of Defense agency, and in 2001, a 19-year-old hacker nearly destroyed one of North America’s largest ports with a denial-of-service attack. (You can read about these teen hackers and others here.) Their contributions to society aren’t exactly positive, but it’s undeniable that they’ve challenged information technology specialists and made Web security stronger by making complacency impossible.

But rebellion has recently taken another form that was more positive: rebellion against George W. Bush and the very notion of politics as usual. Obama rode to the presidency on a wave of youthful energy, and his supporters reinvented the art of campaigning—out with party machines, in with small donations and social networking. Even some of his top strategists were in their early 20s, such asChris Hughes, who had helped create Facebook as a teen.

It remains to be seen whether the Obama presidency will be judged a success, but the youthful rebellion had a profound effect: Campaigns will never look the same.