A new program will soon be released which can scan social networks for pictures of particular individuals.
Israeli company face.com has been testing a product which works by scanning a face and matching the relative positions of eyes, nose and mouth to photos that it reckons could be of the same person. It's claimed to have 90 percent accuracy.
It's not dissimilar to the search features in Google's Picasa - but with the rather notable difference that it performs this search online.
The service is ringing alarm bells among privacy campaigners.
"Ultimately we have to take a degree of personal responsibility for our online identities and how much we place on the internet," says Dylan Sharpe of Big Brother Watch.
"Nevertheless, the people who will be most affected by software such as this are the young children and teenagers who have embraced social networking to its fullest. They are also the demographic least aware of the dangers and the value of privacy."
"Face recognition is a two edged sword. On the one hand the technology can be a tool to track what people are doing with your image. On the other, it can be used to track you and to create a comprehensive profile," says Simon Davies, director of Privacy International.
"The gravest danger emerges when the technology falls into the hands of stalkers or those with criminal intent. However it's most likely it will be used by tax authorities, police, local government and insurance investigators."
The developers say the program only scans photos to which people already have access, through already being Facebook Friends, for example.
"For Facebook photos and users, Face.com uses Facebook’s platform APIs and the user's Facebook Login credentials to mirror the Facebook privacy settings of you and your friends and gain access to information each time it is used," says the company.
"For example, if you choose to hide your Facebook tags, our services will get blocked out when attempting to recognize you in photos."
And when it comes to scanning the web for photos, face.com says it limits the number of pictures that can be processed per hour, making stalking unfeasible... although that might depend on how long a stalker was prepared to spend on the job.
And there's already an application called Celebrityfindr available based on the technology, which looks for celebrities - as well as lookalikes, of course - on Twitter.
"At the moment there's very little if any legal protection to control use of the technology. This has to change," says Davies. "Face recognition is the next wave of internet surveillance, and regulators haven't even grasped the basics of the software."