Facebook Inc., the social networking company that began trading its shares on May 18, has been sued for a whopping $15 billion in an amended complaint by users who accuse the company of invading their privacy by tracking their Internet use.

A class action lawsuit filed against Facebook consolidates 21 lawsuits nationwide. In the complaint filed Thursday, May 17, in federal court in San Jose, California, the plaintiffs claim Facebook abusively tracked subscribers even after they logged out.

The latest filing seeks to proceed on behalf of U.S. residents who joined the social network from May 2010 to September 2011. A German official has also expressed concerns regarding Facebook's privacy approach.

21 Privacy Lawsuits in a Single Case

The lawsuit was filed by law firm Stewarts Law US, and consolidates 21 privacy suits filed against Facebook in more than a dozen states. The case started with accusations made back in September 2011 that the social networking company improperly tracks user activity even after users have left the site.

According to Stewarts Law, the $15 billion figure was established using statutory damages set by the federal Wiretap Act, which "provides statutory damages of the greater of $100 per violation per day, up to $10,000," according to the complaint. The lawsuit also accuses Facebook of violating the Computer Fraud and Abuse Act, the Stored Communications Act, California common law and various California statuses, as eWeek points out.

'Groundbreaking Digital Privacy Rights Case'

"This is not just a damages action, but a groundbreaking digital privacy rights case that could have wide and significant legal and business implications," Stewarts Law partner David Straite said in an emailed statement to Bloomberg.

During the past few years, Facebook has been under scrutiny both in the United States and abroad, over its approach on privacy controls and policies. A German data protection agency expressed concerns last year regarding Facebook's use of facial-recognition technology for tagging photos. Moreover, the German agency threatened to fine Facebook for unauthorized data collection.

User Privacy Controls

A recent study conducted by Consumer Reports found that roughly 13 million Facebook users in the U.S. either do not use or are not aware of the site's privacy controls. Furthermore, 28 percent of the people polled said they share either all or nearly all their Facebook activity with people beyond their "friends" circle. Meanwhile, only 37 percent reported having used the site's privacy tools to limit how much information they share with apps.

"Facebook really is changing the way the world socially communicates and has become a successful service in part by leveraging copious amounts of personal data that can be spread far wider than its users might realize," Consumer Reports technology editor Jeff Fox said at the time, as cited by eWeek. "Our investigation revealed some fascinating, and some disquieting trends - but ones always worth knowing for consumers who wish to keep their personal data under better control."

Not so long ago, Facebook was also involved in the great controversy revolving the "Girls Around Me" app, which combined Foursquare and Facebook data to offer a user a detailed map of available "prey" nearby. The people who were displayed on the map had no idea that their entire Facebook profiles were displayed on some dude's phone nearby. The issue stirred some serious controversy at the time, and emphasized the importance of privacy controls. Facebook claims more than 900 million users as of May 2012.

This is not the first lawsuit of the kind, but none of the previous suits were successful because cookies are not considered a violation of wiretap laws. "We believe the complaint is without merit and we will fight it vigorously," said a Facebook spokesperson in a statement to the press.