In papers filed this week with the federal district court in New York, the American Library Association, Association of College and Research Libraries and Association of Research Libraries are asking for "rigorous oversight" of the settlement agreement.

The groups, which represent more than 139,000 U.S. libraries, argue that the agreement could leave Google too powerful in the nascent digital books market. The associations also specifically warn that the settlement does not adequately protect users' privacy.

The agreement allows Google to digitize books and sell downloads at prices it sets in conjunction with a new book rights registry (which Google will fund). If the settlement is approved, it would resolve a lawsuit filed by the Authors Guild and the Association of American Publishers in 2005, alleging that Google infringed copyright by digitizing books.

The libraries are concerned because Google will collect personal information from buyers, but isn't obligated to keep those records confidential. "The settlement is silent concerning what information Google will retain concerning the consumer, how it will use the information, and what measures it will take to protect the information's security," the associations state in their friend-of-the-court brief.

The groups aren't objecting to the deal, but have asked U.S. District Court Judge Denny Chin to oversee it closely.

The digital rights group Electronic Frontier Foundation also has concerns about whether Google will adequately protect users' privacy. Cindy Cohn, legal director of the group, says the group will represent writers who are worried that their readers won't want to purchase books without assurances of confidentiality.

"Authors whose readers depend on anonymity will be hurt if there's not sufficient protection for privacy here," Cohn said. For instance, she said, writers who deal with sensitive topics -- such as sex or drug policy -- want assurances that their readers' names will remain confidential.

Cohn said the EFF intends to object to the settlement in its current form. But, she said, she believes the deal could be fixed if Google and the authors and publishers "commit to a privacy policy and a structure that protects people's privacy."

The library groups also say they fear the deal could "stifle intellectual freedom" because Google would only have to make 85% of the in-copyright books it has scanned searchable. "While Google on its own might not choose to exclude books, it probably will find itself under pressure from state and local governments or interest groups to censor books that discuss topics such as alternative lifestyles or evolution," the libraries argue.

Google has said the settlement will benefit authors, publishers and readers, because it will result in expanded access to books.

Nonetheless, the deal is drawing increasingly vocal critics. Among others, advocacy group Public Citizen opposes a portion of the settlement, as does Consumer Watchdog. Additionally, New York Law School intends to file a brief asking for antitrust oversight of the deal. Last week, it also came to light that the Justice Department was making inquiries about the settlement.