The protesters complain that the RSS feed publicizes potentially embarrassing developments including romantic breakups, friendships going sour, professional setbacks, and the like. Even though this information was available before, Facebook's active spreading of it via RSS feeds offended hundreds of thousands of the site's users.

As of Wednesday night, more than 290,000 of the site's 9 million members had joined a group called "Students Against Facebook Newsfeed," and their dissent has begun cascading from Facebook to other online forums.

Site founder and CEO Mark Zuckerberg appears to have been blindsided by the user backlash. In a blog post Tuesday night, he told members the company was "listening" to member suggestions, but added that all of the information included in the RSS feeds was publicly available anyway. "The privacy rules haven't been changed. None of your information is visible to anyone who couldn't see it before the changes," he wrote. "Nothing you do is being broadcast; rather, it is being shared with people who care about what you do--your friends."

Nonetheless, many members are extremely vocal in their anger toward the company. One petition presented by "Students Against Facebook Newsfeed," and signed by 40,000 users, noted the "unprecedented outpouring of opposition to the changes within the community," and demanded either "the immediate removal of the 'news feed' and 'mini feed' feature from Facebook.com," or that Facebook "[a]llow an individual to remove himself or herself from the "news feed" and "mini feed" feature on other users' page."

Similarly, a student-run portal for the University of Mary Washington in Fredericksburg, Virginia, gave center stage to the complaints. "We all awoke this morning scared and confused. Girlfriends and boyfriends alike went on the prowl, and many became upset," stated the Web site. "We really dislike the new Facebook and [its] unsafe and uncool feature known as 'Feeds.' It's simply organized gossip, but everyone feels the effects of it."

The strength of the protest has taken even veteran industry observers by surprise. Pete Blackshaw, chief marketing officer for Nielsen//BuzzMetrics, said he'd never seen such a large, rapid or concerted "attack-back" by consumers. "This is clearly unprecedented," Blackshaw says. "It's a remarkable spontaneous combustion of protest--they're building this sort of consumer cartel of discontent around this issue," he says.

Above all, Blackshaw said, the Facebook mishap proves that "these CGM venues are very, very delicate and fragile from a user reaction perspective. Changing stuff can have a real downside, because there's always the potential for consumers to rise up and revolt and out-CGM you."

The growing chorus of user dissent also illustrates the power--and potential marketing downside--of viral campaigns: the same infrastructure that allows popular content to proliferate across the Web at lightning speed also enables spectacular and breathtakingly fast consumer backlash.

"This is the beauty and the evil of viral marketing right here," says Rachel Honig, co-founder of the digital-marketing firm Digital Power & Light. "The beauty is you can get 60,000 people to sign the petition in a day--but honestly most of them are just kind of following along."

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