More than 100,000 people have "liked" or commented on the photo, which had the caption "Subway pls respond." Lookalike pictures popped up elsewhere on Facebook. And The New York Post conducted its own investigation that found that four out of seven footlong sandwiches that it measured were shy of the 12 inches that makes a foot.
The original photo was no longer visible by Thursday afternoon on Subway's Facebook page, which has 19.8 million fans. A spokesman for Subway, which is based in Milford, Conn., said Subway did not remove it.
Subway also said that the length of its sandwiches may vary slightly when its bread, which is baked at each Subway location, is not made to the chain's exact specifications.
"We are reinforcing our policies and procedures in an effort to ensure our offerings are always consistent no matter which Subway restaurant you visit," read an e-mailed statement.
The Subway photo — and the backlash — illustrates a challenge companies face with the growth of social media sites like Facebook, YouTube and Twitter. Before, someone in a far flung local in Australia would not be able to cause such a stir. But the power of social media means that negative posts about a company can spread from around the world in seconds.
"People look for the gap between what companies say and what they give, and when they find the gap — be it a mile or an inch — they can now raise a flag and say, 'Hey look at this,' I caught you," said Allen Adamson, managing director of branding firm Landor Associates in New York.
Subway has always offered footlong sandwiches since it opened in 1965. A customer can order any sandwich as a footlong. The chain introduced a $5 footlong promotion in 2008 as the U.S. fell into the recession, and has continued offering the popular option throughout the recovery.
An attempt to contact someone with the same name and country as the person who posted the photo of the footlong sandwich on Subway's Facebook page was not returned on Thursday.
But comments by other Facebook users about the photo ran the gamut from outrage to indifference to amusement. One commenter urged people to "chill out." Another one said she was switching to Quiznos. And one man posted a photo of his foot in a sock next to a Subway sandwich to show it was shorter than a "foot."
"I've never seen so many people in an uproar over an inch. Wow," read one Facebook post. "Let's all head to McDonald's and weigh a Quarter Pounder," suggested another poster.
The Subway footlong photo is just the latest in a string of public relations headaches that were caused by a negative photo or event about a company going viral.
Last year, a Burger King employee tweeted with a picture of someone standing in sneakers on two tubs of uncovered lettuce. Domino's Pizza employees posted a video on YouTube of workers defacing a pizza in 2009. And a KitchenAid employee last year made a disparaging remark about President Obama using the official KitchenAid Twitter account.