The gig: Joe Green is the 26-year-old founder and president of Causes, an organization that offers a popular Facebook application encouraging people to contribute time and money to their favorite cause. Green launched the Berkeley-based Internet start-up in 2007 with former Facebook executive and Silicon Valley veteran Sean Parker.
Together they built a thriving marketplace for social and political causes on Facebook, the popular social network started by Green's Harvard roommate, Mark Zuckerberg. Causes helps all nonprofits, but especially smaller ones that cannot afford direct mail campaigns. "The goal is equal opportunity activism," Green said.
How it works: Facebook users install a program called Causes. Facebook friends band together to solicit donations, promote advocacy and spread awareness for a cause.
The Internet is unparalleled in its power to quickly rally -- and pressure -- far-flung friends to participate, Green said. For example, with Causes' popular birthday wish feature, users can ask their friends to donate money to a cause in lieu of presents. The birthday feature raises $20,000 a day for various causes.
Petitions are also effective. One petition to get insurance companies to cover genetic testing for breast cancer garnered nearly 3.5 million signatures. Causes does not take a cut of donations, but users can tip the service.
Causes also makes money from causes that are sponsored by nonprofits and others trying to reach more people, banner advertising and premium services that help nonprofits get more out of using the service.
The results: No gusher of funds for nonprofits yet, but Green has made significant progress in his quest to invent a new model for philanthropy. Causes has recruited 100 million Facebook users who have created 400,000 causes since May 2007.The median donation is $25. In all, Causes has raised $21 million for charity.
Early bloomer: Green was inspired by his grandfather, trial lawyer Irving Green, who pioneered product liability law in California and made his life's work representing the underprivileged. He died when Green was 8, but his social conscience lived on in Green's father, Mark Green, a UCLA math professor.
Joe Green, who grew up in Santa Monica, became a community organizer at a young age. In high school, he took a non-voting seat on the Board of Education. He also campaigned for a living wage for Santa Monica hotel and restaurant workers.
"The most important thing we can do as a society is to make sure that people who are not from powerful backgrounds have an honest-to-God chance to be successful," Green said.
At Harvard, he studied with Marshall Ganz, who has helped spark a resurgence in grass-roots organizing in Democratic campaigns, including Obama's historic presidential run. From Ganz, Green learned the importance of sharing personal narratives in building social movements.
From politics to the Internet: While campaigning for Democratic presidential candidate John F. Kerry during college, Green said he realized that an online social network could revolutionize political organizing.
He tried to persuade Zuckerberg to create a social network for politics, but Zuckerberg launched Facebook instead. Green was an early advisor to Facebook.
In 2004 it was his job to respond to e-mails from Facebook users looking for polling places to cast their vote. That summer, he worked for Kerry as a field organizer in rural Arizona. He knocked on doors in 120-degree heat with a group of volunteers, retired truckers, power plant workers and office managers.
"The experience made me believe in democracy," Green said.
Taking action: In 2005 he created a site called Essembly, a nonpartisan social network that enables people to connect with others who shared their political views and take action.
After meeting Parker through Zuckerberg, the pair spent the summer of 2006 brainstorming in a coffeehouse in Hollywood (where they were frequently distracted by celebrity blogger Perez Hilton).
Together they decided to use social networking to incite activism on a broader scale. Causes launched in May 2007.
Within a few weeks, it hit 1 million users, becoming one of the most popular applications on Facebook.
Causes raised $7.5 million in capital, including foundation money from two prominent philanthropists, Steve Case and Ray Chambers.
Best management advice: "I think of managing talented people as managing volunteers. They could get another job easily, so it is my job to make sure they are supported in every way possible, and get out of the way."
Best moments: Causes has taken Green to Tanzanian villages with singer John Legend and to the Bush estate in Kennebunkport, Maine. (He and Neil Bush are now friends on Facebook).
But his most rewarding moment was the America's Giving Challenge, which Causes helped organize.
Nonprofits competed for $245,000 over 30 days, spurring thousands of people to raise more than $2.1 million for their favorite causes.
"We are empowering new donors," Green said. "The idea that anyone can be a philanthropist is very powerful. It's not just something rich people can do."