Netflix will introduce “social features” for U.S. users in 2013 — assuming President Obama signs a law that would make it legal to do so — but the features laid out in the terms of service the company amended this weekend don’t appear to meet with current industry best practices, according to privacy advocates.

Sharing video rental histories was previously illegal in the United States, thanks to a law enacted after the media revealed Judge Robert Bork’s video rental history during his controversial and ultimately unsuccessful effort to be confirmed as a Supreme Court Justice in the mid-1980s. Netflix has lobbied aggressively to have the law amended.

Netflix confirmed that it will launch social features if the law changes, but declined to provide details about how its proposed sharing features would work. But the updates it made to its user agreements this weekend provide a few hints.

According to the new terms, users who link their Netflix and Facebook accounts automatically give their friends access to their entire movie-watching history, unless they manually disable the feature for particular films.

“[I]f you connect your Netflix account to Facebook, we will access information about you and your Facebook friends on an on-going basis, unless you disconnect. We will import, use, disclose and retain this information to, among other things, customize and improve the Netflix service for you, your friends and others. In addition, by connecting your Netflix account to Facebook, we will automatically post your activity to Facebook, including what you watched,” the company said the section of its updated policy dedicated to Facebook. Users in other countries were already able to share viewing histories on Facebook.

“Your friends and others who have access to view information about you on Facebook will … be able to see (on Facebook and on Netflix) that you’re a Netflix member as well as what you’ve watched, and other information about your use of the Netflix service,” the terms also say.

To adhere to the law, Netflix will have to provide users with a “clear and conspicuous” option to stop sharing and will also have to reconfirm that users want to continue sharing every two years, according to Sarah Downey, an attorney with the online privacy company Abine.

The effects on user privacy will depend on how Netflix implements the features, said Justin Brookman the director of the Center for Democracy and Technology’s Project on Consumer Privacy.

“Users already have active Netflix accounts tied to credit card information, so they’re unlikely to be confused as to why they’re connecting. [Because] they’re not using Facebook just for login credentials, it will likely be an affirmative decision to link the accounts for the purpose of sharing,” Brookman said.

But he added that Netflix should offer users, such as those who simply find Facebook Connect more convenient, options to turn off sharing altogether or share only those movies they manually opt to post to their Facebook timelines.

Users may not be aware of how much their viewing history reveals about them, Downy said. She pointed to a study in which researchers linked anonymous Netflix account-holders with real identifications and were able to glean insight into “their apparent political preferences and other potentially sensitive information.”

“Automatically sharing everything you watch could dissuade people from watching more controversial but valuable things, like political or religious documentaries,” Downey said.