Consumers groups have sent a letter to the Federal Trade Commission, charging that a new marketing program launched by Facebook violates the terms of the social networking site’s settlement with the agency earlier this year.

In August, the agency finalized a settlement with Facebook over allegations that the company made user information public by default, even though the company promised to keep the information private.

Just one month later, the Electronic Privacy Information Center (EPIC) and Center for Digital Democracy (CDD) sent a letter to the agency seeking an investigation into a new “data-matching” deal the site recently launched with Datalogix.

A data-mining company, Datalogix collects consumer information from offline retailers that includes names, addresses, e-mail addresses, and behavioral information like purchase history. The agreement allows Datalogix to match its database with Facebook user information with the goal of profiling consumer offline commercial activity, according to the letter.

This sharing of information violates the site’s consent decree with the FTC, under which Facebook was required to make “clear and prominent” disclosures and obtain affirmative consent from users prior to the sharing of any user’s nonpublic information, the letter argues. Neither Facebook’s data use policy nor its statement of rights and responsibilities explains that the information is disclosed, and the one reference to Datalogix is difficult to find, the groups argue. The page where it is located “requires at least five actions to reach from the home page and simply directs users to the Datalogix privacy policy.” The failure to notify users constitutes a misrepresentation by omission in violation of the consent agreement, they contend.

In addition, although Facebook said that the data will all be hashed and that no individual user’s information will be shared, the anonymization technique is “vastly overrated,” the groups wrote, expressing concern that the data would not be matched anonymously.

Finally, the opt-out language for the program is “confusing and ineffective,” according to the letter, and “hidden within Datalogix’s long privacy policy.” Opting out also requires an opt-out cookie, the groups said, which users often delete, not realizing they have removed the record of their request to be treated anonymously.

To read the letter to the FTC, click here.

Why it matters: Facebook remains a lightning rod for privacy issues. The social networking site’s agreement with the FTC was barely finalized before EPIC and CDD sent their letter to the agency alleging violations of the agreement. It remains to be seen whether the FTC investigates the data-matching arrangement between Datalogix and Facebook.