'Someone's always watching': internet vigilantes spark privacy fears

She was not the sort of dog to stray. So when Buckie the British Staffordshire bull terrier went missing from the driveway of her Bondi home, her owner, Grace Barnes, started searching the streets and beyond.

She put up posters offering a $1000 reward for her purebred pup. Her Facebook page – Help Us Find Buckie – has drawn hundreds of people into the hunt, among them a psychic "animal communicator" from Germany.

But things took a novel turn when Barnes, a 28-year-old naturopath, spotted a security camera outside a building near her apartment. She approached the building manager, who let her watch and copy CCTV footage from last week that appears to show a boy with short, brown hair in a sports jumper carrying Buckie down the street.

Barnes posted the grainy footage on Facebook and a childhood friend who saw it then contacted her with details of someone resembling the young teenager and his secondary school, in Sydney's eastern suburbs. Police plan to interview the boy and his mother today.

"Someone's always watching, that's the thing to remember. You can't get away with anything these days," Barnes said.

But the NSW Deputy Privacy Commissioner, John McAteer, criticised the increased use of social media and CCTV footage by the public to catch alleged criminals. "It's concerning that people would post images of children online without the consent of a responsible adult," he said.

"Law enforcement is a matter for law enforcement bodies and members of the public shouldn't be taking matters into their own hands."

Social media is being used more often to identify alleged offenders or find people who are missing. Images posted on Facebook of four-year-old Nambucca Heads boy Riley Martin helped find him after he went missing this month.