Facebook risks an inevitable privacy backlash when it launches a feature that shares information on the location of users with their online friends, despite devising a range of controls that require users to opt-in to the service.

The feature allows users to “check in” at locations which will then be shared with their friends and Facebook network but it is likely to raise concerns over safety. Users will also be able to browse shops, clubs and nearby venues to see which friends are nearby, leading to concerns it could put individual's security at risk.

“What we see with Facebook is a massive learning curve. Every time they make a change, consumers scramble to figure out the privacy settings,” said Rainey Reitman, spokeswoman for Privacy Rights Clearinghouse in the US. “Location data is tied to people's safety - if people know where you are, they know where you're not. Your location data is some of the most sensitive data we have. I expect we'll see from the get-go people who don't understand how to control the privacy settings.”

The service will launch in the US only at first. Reitman said users should be particularly judicious about who they accept as friends, and be aware that even information shared with an intimate network could be copied and pasted elsewhere. “Don't post anything online you wouldn't want to get out publicity to anyone.”

After a string of controversies around the safety of the site, Facebook simplified its privacy settings in May and will be acutely aware of the scrutiny to which its new location feature will be subjected. Facebook Places product manager Ana Yang said the site encourages users to take control of the connections they have on the site. “People are already sharing their location on Facebook, so we looked at this to see if we could make it easier, more consistent and more social,” she said.

“But if it means removing friends you don't know or even blocking someone, we support all those things because you'll have more control. People should be establishing the social norms that it's OK to block the sketchy ex-boyfriend and in some ways it's easier to do this on Facebook than in real life.”

Yang said protections include notifying a user as soon as they are tagged at a place, and offering a complete opt-out of “places” tags. Users under 18 can only share location with their immediate friends network and their real-time location will only be seen by friends at the same location.

“We believe that if you can control the audience you are sharing with, you will be more willing to share,” said Yang. “We equate it with this existing mechanism where your friends can tag in photos - the control is that you are always notified and can remove those tags at any time.”

Critics will note that once a user decides to check in at a location, the primary location setting is switched on by default, which means any “places” tags automatically being shared with immediate friends. But the service does offer a range of protections and controls including the option to detag locations, notifications if friends add your location and the option to disable Places entirely.

Facebook's solution to the challenges of location services had been hotly anticipated by Silicon Valley. Web and mobile developers have been exploring location-based features for several years but the combination of widespread smartphone take-up has allowed services such as Foursquare and Gowalla to flourish.

Facebook has been watching the development of these services, which are setting up a steady stream of promotions and prizes with venues and retailers to reward loyal customers who “check in” regularly. In the US, Starbucks used a Foursquare promotion to attract a million customers to its stores in a day, while UK Domino's stores offered free pizza to “mayors” - Foursquare users with the most points.

Andrew Scott has been experimenting with location tools since 2002, and co-founded the personalised recommendations tool Rummble. “There have been big changes in the way we communicate with brands,” he said. “That has been fuelled by Twitter, which made it credible that people could communicate with brands more directly, and Facebook's “like” button, which made it credible that information could be personalised.”

Initially available as an update to Facebook's app for Apple iPhone, updated apps for BlackBerry, Android and other handsets are expected in the next few months. A version will also launch for the UK, where research by the communications regulator Ofcom found that 45% of web browsing time on UK mobiles is spent on Facebook. Nearly one-third of Facebook's 500 million users access the site by mobile, it claims. —Dawn/Guardian News Service