California: Images on Facebook are no longer safe, thanks to the new facility of tagging friends. The 'Tag Suggestions' system uses facial recognition software to identify individuals as photos are uploaded, and then encourages their friends to tag them so that others can easily access the images.

Facebook has quietly rolled out face recognition technology to users around the globe, which automatically picks out friends from newly-uploaded photographs and recommends suitable name tags.

The service, which debuted to some users in the US earlier this year, is all about making tagging photos less of a chore. "Like that time you had to tag your cousin and her fiance over and over and over again in 64 different pictures of their engagement party," reminds Facebook engineer Justin Mitchell.

Facebook originally began testing Tag Suggestions in the US only, in December, but has now extended it to "most" of the dominant social network's 700 million users worldwide without notice.

"Yet again, it feels like Facebook is eroding the online privacy of its users by stealth," said Graham Cluley, of the British internet security firm Sophos.

"Many people feel distinctly uncomfortable about a site like Facebook learning what they look like, and using that information without their permission."

Marc Rotenberg, executive director of the Electronic Privacy Information Center in Washington DC, criticised the way Facebook had opted users into its facial recognition system by default.

"I'm not sure that's the setting that people would want to choose. A better option would be to let people opt in," he said.

Facebook has frequently pushed its users to reveal more online by implementing new features by default. Facebook Places, a location-based service launched last year, broadcasts some information about users unless they explicitly tell it not to, for example.

Following the criticism of Tag Suggestions, Facebook said, "We should have been more clear with people during the roll-out process when this became available to them".

It added that the facial recognition technology would only be applied to newly-uploaded photos.

Users can disable the feature by turning off the "suggest photos of me to friends" option on their Privacy Settings page.

Facebook has previously faced criticism for the complexity of it its privacy settings and following yet another privacy controversy in May last year Mark Zuckerberg, its CEO, pledged to make them simpler.

How to turn it off
Built straight into the privacy settings (click your 'Account' link), users should go to a link that says 'Customize Settings.' Under the section 'Things others share,' there's an option labeled 'Suggest photos of me to friends.'

Disable this feature, and Facebook will no longer suggest you as tag-able when your friends get a little too photo happy. However, it doesn't stop them from tagging you altogether they can still do it manually.