What the site didn't explain is that the Beacon feature would track purchases on other Web sites and then broadcast that information to people's friends.
The move unleashed a vitriolic and rapidly expanding protest on privacy issues, spearheaded by the political group MoveOn.org.
"When you buy a book or movie online -- or make a political contribution," reads MoveOn.org's call to arms, "do you want that information automatically shared with the world on Facebook?"
The issue, says blogger Sara Robinson of GroupNewsBlog, is that Facebook's Beacon tracks people, then announces their choices, whether it's a sexy movie or holiday shopping online. Robinson compared Facebook to "a Grinch so big that the good Dr. Seuss himself would have been gobstopped by the sheer magnitude of it all."
"Oh my gosh," Tasha Valdez wrote on a Facebook protest discussion board. "My cousin's entire Christmas shopping list this week was displayed on the (Facebook News) feed. That's so messed up."
Scotts Valley resident Kevin Driscoll, a Yahoo staff member with three grown children, hasn't had his purchases trumpeted on Facebook.
That's the crux of the matter. Users cannot opt out of Facebook Beacon without clicking "no thanks" every time they make a purchase from a participating vendor, and they're having trouble finding the place to do that. Moreover, it's difficult to discover who, exactly, the 40 or so vendors are.
BustedTees.com and the New York Times confirm their involvement. Other lists floating around the blogosphere include Fandango, Blockbuster.com, eBay, Sony and Travelocity. Another company frequently -- though inaccurately -- associated with Beacon is Amazon. Amazon spokeswoman Patty Smith denied that the company was involved. She says the company had no plans to sign on, and she expressed her frustration about bloggers using Amazon as a what-if example.
Facebook has tried to give the advertiser-boosting service a quirky, user-friendly spin.
"Adding the first season of 'Buffy the Vampire Slayer' to your queue on Blockbuster.com might be something you want your friends to know about," Facebook ad program manager Leah Pearlman wrote in her blog Nov. 6, the day Beacon was released, "so you can have a marathon."
Justin Rosenstein, technical lead for Facebook Beacon, referred all media calls to Facebook's public relations director, who did not respond. But Rosenstein has a blog entry that describes the ease with which users can opt out of publicizing their purchases, one transaction at a time.
The odd thing is, a few days before the new Facebook feature went live, TechCrunch.com posted screen shots of the beta version that clearly gave users the ability to opt out of publicizing some or all of their purchase information by vendor. That option no longer exists.
"There is no permanent opt-out option," said MoveOn.org spokesman Adam Green, "let alone an opt-in policy. They proactively took it out."
The protests are growing. One protest group -- "Facebook, stop invading my privacy!" -- has amassed more than 24,000 members, including students from UC Berkeley and Stanford and Tamalpais and Berkeley high schools, in the past six days.
MoveOn.org hopes that Beacon will follow the path of News Feeds, Facebook's last user snafu. It was just more than a year ago that the social network began blasting out headlines, so to speak, on its members' breakups and hookups the moment their friends logged on. After more than 700,000 users joined a Facebook protest group, company founder Mark Zuckerberg issued a public apology -- "We really messed this one up. ... I'd like to correct those errors now" -- and added extra privacy controls.
Some bloggers say Beacon will go the same way. New media specialist Rodney Rumford is not so sure.
People are "passionate" about privacy, said Rumford, but Facebook users need to keep the latest disclosure in perspective.
"Google knows probably more about me than Facebook," he said. "But Facebook has chosen to expose what they know in a way that is maybe a little disconcerting to people. My whole take is people were really overreacting. They have the ability to turn on privacy controls. They just have to do that."
Rumford, whose company helps businesses market themselves on Facebook and MySpace, says he "lives online," spending as many as 16 hours a day on the Internet, working, networking, socializing and shopping. But even Rumford wonders why Facebook didn't post a list of participating sites and offer its users a chance to opt out of the service.
"People could come to like it," he said. "But like any disruptive technology, people knee-jerk back initially."
He compared it to the first time iTunes gave him album recommendations, and he already owned six of the eight.
"It freaked me out," he said.
Then, he decided it was cool.
Reach Jackie Burrell at email@example.com.