New York:  Moments after Facebook introduced a new feature called Facebook Places on Wednesday that allows its users to share their location and find their friends, advocates raised flags over online privacy.

The American Civil Liberties Union of Northern California cited concerns over the new product, saying Facebook neglected to include several crucial privacy features.

The organization highlighted the element of the new service that allows users to “tag” an accompanying friend and post his or her location to Facebook – even if the friend does not have an iPhone, which is currently the only platform on which the application is available.

“Places allows your friends to tag you when they check in somewhere, and Facebook makes it very easy to say ‘yes’ to allowing your friends to check in for you,” read the statement, released late Wednesday night. “But when it comes to opting out of that feature, you are only given a ‘not now’ option. ‘No’ isn’t one of the easy options.”

The A.C.L.U. also expressed concern over the integration of Facebook’s Places feature with third-party Web sites and applications.

“Your friends’ apps may be able to access information about your most recent check-in by default as soon as you start using Places,” the organization said. “Even if you’ve already gone through your settings to limit the info that apps can access, you should do it again — you may find that you’ve been defaulted into sharing your location info with apps.”

The early stirrings of concern are reminiscent of the Facebook privacy debacle that erupted a few months ago after the company revised its platform that encouraged members to make personal details accessible more broadly on the Internet. After a string of frustrations, the company simplified its privacy settings in an effort to make the controls easier to navigate.

During a news conference held at the Facebook offices in Palo Alto, Calif., Mark Zuckerberg, chief executive of the company, sought to reassure users about the service, saying it was a “really fun and interesting product.”

“The main thing we are doing is allowing our users to share where they are in a really nice and social way,” he said. “You can see who is around you and connect in the real world.”