Social-action Web site Change.org has emerged as an influential channel for nonprofit groups and activists seeking to promote an array of causes and campaigns, The Washington Post writes in a profile of the growing company.

The firm allows any user to launch a petition drive for free but charges fees to orchestrate campaigns for organized groups, using social media to build momentum for causes. In the past year it helped build consumer rebellions against fees charged by Bank of America and Verizon and enlisted the San Francisco Giants baseball team in the fight against anti-gay bullying, among other successes.

“We’re in the business of amplifying,” Change.org founder Ben Rattray said. “We’re trying to change the balance of power between individuals and large organizations.”

The social-benefit corporation has grown from 20 employees to about 100 in the past year. Mr. Rattray said Change.org is profitable and hopes to boost revenue by tens of millions of dollars within a few years.