By STEPHANIE ARMOUR

Kellogg’s Kashi natural cereal uses some genetically modified ingredients. That was enough to convince an organic grocer in Portsmouth, Rhode Island to pull the brand from his store’s shelves.

Then, a photo of a sign displayed on one of the empty shelves explaining what had happened quickly went viral, lighting up the Web. Kellogg Co. (K)’s Kashi unit responded last week with a video on Facebook (FB) defending its use of the ingredients. By then, however, the noise level was rising, with some online groups threatening a boycott.

It was just the latest skirmish in an escalating Internet- based uprising. Facebook, Twitter and petition sites like Change.org have birthed a brand of consumer activism that lets people rally supporters under a common cause at breakneck speed. The tactic has caught on in a big way, taking on one company after another, putting practices under a spotlight: bug extracts at Starbucks Corp. (SBUX), livestock antibiotics at Cargill Inc. and the treatment of animals by McDonald’s Corp. (MCD)

“It used to be the most power you had was writing your congressman” and waiting, said Amanda Hitt, director of the food integrity campaign at the Government Accountability Project, a Washington-based public advocacy group. “Now petitions are becoming an especially powerful tool.”

That tool has proven especially effective against lobbying efforts among lawmakers. Agribusiness, for instance, spent id=”mce_marker”24 million in 2011 on lobbying, up from $77 million in 1999, said the Center for Responsive Politics in Washington.

Mad Cow Disease

Following last month’s discovery of a case of mad cow disease, online petitions at Change.org began popping up to demand that the U.S. allow cows to be fed only a vegetarian diet and that all beef be tested for the disease.

In March, a coalition called the Just Label It campaign submitted 1.1 million names — about the population of Dallas — to the Food and Drug Administration calling for genetically- modified food to be labeled.

The upside of these petition drives “is it forces the attention of the government and politicians,” said Rohit Bhargava, senior vice president of the global strategy and planning group at Ogilvy in Washington. The downside is that “people can combine efforts around things that aren’t really facts,” he said in an interview.

No recent social media campaign has captured consumers’ imagination in quite the way the “pink slime” controversy has. The idea struck blogger Bettina Elias Siegel in the kitchen of her home in Houston. Ammonia-treated beef scraps were showing up in hamburgers in U.S. schools, a “pink slime” that the former lawyer saw as risky to children.

260,000 Signatures

The mother of two started a petition on March 6 on Change.org, garnering almost 260,000 signatures. In less than two weeks, the U.S. Agriculture Department said it would let schools order beef without the scrap meat. By April 2, Beef Products Inc., the biggest producer of the so-called lean, finely textured ground beef, had closed three plants, while Yucaipa Cos.’s AFA Foods Inc. cited the controversy as a factor pushing it into bankruptcy.

“Bettina’s petition just exploded,” said Sarah Ryan, a campaigner at San Francisco-based Change.org, a social action website. “It’s really given the consumers the motivation they need to realize they can change the food industry.”

BPI has been making lean, finely textured beef for three decades and said it’s worked to inform consumers about the product’s safety. The Dakota Dunes, South Dakota-based company puts beef trimmings in a centrifuge to separate the meat from fat and then uses ammonium hydroxide to kill pathogens such as E. coli.

Internet Democracy

“Our company has faced unprecedented and often unfair coverage in the media,” BPI said in a statement. “We have done our best to set the record straight on a product that is not only safe, but an extremely effective way to make lean ground beef available to consumers using 100 percent beef.”

BPI will have to become more savvy in responding to social media campaigns, said Bill Marler, a Seattle food safety lawyer. BPI took too long to support its product after Siegel’s petition and media stories gained momentum, he said.

“It’s not bad to get people engaged, but it’s going to require more engagement from the other side,” Marler said in an interview. “Information is now instantaneously available, so you have to come up with a different strategy of managing the Internet democracy.”

‘Disgusting’ Opinions

More than 6,500 people signed a Change.org petition asking Starbucks to stop using dried insects to color products such as Strawberries & Creme Frappuccino. The petition urged the Seattle-based coffee retailer to drop the red dye made from female cochineal insects because it isn’t vegan and consumers “don’t want crushed bugs in their designer drinks.”

Supporters have added comments such as “the idea of eating bugs without knowing…well, it’s kind of gross,” and “bugs!!?? Disgusting!!”

Starbucks bowed to pressure on April 19, saying it would switch to lycopene, a tomato-based extract, by late July in U.S. stores. Starbucks takes feedback from social media channels seriously, Linda Mills, a spokeswoman, said in an e-mail. The company is moving away from the cochineal extract, which had been used in products including raspberry swirl cake, red velvet whoopee pie and two beverages.

“As our customers you expect and deserve better, and we promise to do better,” Cliff Burrows, Starbucks president for the U.S. and the Americas, said in a news release.

Siegel, the mother who started the pink slime petition, said she was wowed by the public response to her cause.

“Greater transparency in our food supply is always a victory for consumers,” Siegel said in an e-mail. “Though I’m a blogger and use social media all the time, nothing could have prepared me for the astounding reaction my petition received.”