Hundreds of years of technological innovation and here we are: a machine that can tell a Witherspoon from a Kidman.

Both the New York Times and Sky News in the UK used Amazon's machine-learning platform to identify guests at the Royal wedding in May, but for some, this clever deployment points to a more worrying trend.

Critics are concerned facial recognition is being democratised, thanks to tools like Amazon's Rekognition, which they fear are too cheap, too easily available and could be misused.

Some smartphone manufacturers already use facial recognition to unlock phones. ( Reuters: Stephen Lam )

The New York Times is experimenting with Rekognition to help identify public figures and celebrities, a spokesperson said, within the boundaries of applicable laws. It is also using the tool to spot members of Congress.

These are public situations where people might expect to be recognised. What happens when this technology is used on the rest of us?

From the good — such as finding lost children at an amusement park, as an Amazon spokesperson claimed — to ways that are decidedly more questionable.

"If the guests at the Royal wedding would otherwise have been recognisable by the star-spotters, it's a little bit less of an issue," said Dr Suelette Dreyfus, a security expert at the University of Melbourne.

"That's very different from whether a company is secretly tracking your Saturday afternoon walk to the bottle shop to pick up a cold one — then on-selling that information."

Facial recognition, 'democratised'

Companies such as IBM and Microsoft also have facial-recognition technology, but on Amazon Web Services (AWS), it comes at an affordable price.

In Australia, Rekognition video analysis costs $0.13 for one minute of archived video analysed, or $0.013 per 1,000 "face metadata" files stored per month, according to the website.

Rumman Chowdhury, who leads Accenture's responsible AI initiative, said making such powerful tools easily available can be a "Pandora's box".

"People will rely on the datasets that they can cheaply and easily access," she warned.

Amazon says Rekognition has trained its algorithms on a limited list of celebrities.

Celebrity spotting is not the only service it provides. Customers can also build facial-analysis tools (spotting gender, smile, emotions and eyeglasses, among other attributes), compare faces and create a filter to weed out explicit imagery.

Facial recognition technology is already being used around the world. ( Supplied )

Facial recognition typically looks at a face's unique characteristics, such as the distance between chin and forehead, and matches those measurements against a database.

However, Ms Chowdhury pointed out some facial-recognition systems have been shown to have a racial bias, thanks to training data that skews towards dominant social groups.

A recent MIT Media Lab study found certain systems (not Amazon's) were 99 per cent accurate about gender when analysing photographs of white men, but misidentified 35 per cent of images of darker-skinned women.

Such results raise a significant question: Could these tools be used to fairly replace paper tickets at a football game, as some companies have suggested? Or to allow you entrance to an office building?

"There is big leap between CCTV footage — in itself intrusive in public spaces — and the application of facial-recognition software," Dr Dreyfus said.

"This is customised mass surveillance — that is also highly automated and therefore cheap."

A lack of safeguards

Australia doesn't yet have strict rules governing the use of such machine-learning tools, said Human Rights Commissioner Edward Santow.

"We should have a set of principles that developers like Amazon and others are encouraged, if not required, to use," he said.

Australia is also set to introduce a system that will allow government agencies and some private organisations, such as banks, to access a national facial-recognition database.

In a submission to the Parliamentary Joint Committee on Intelligence and Security, the Australian Human Rights Commission said safeguards to protect people's rights and privacy should also be improved.

"We are, I think, at a crossroads in Australia," Mr Santow said.

"The risk is that we sleep-walk into an era where our basic human rights are not protected in this new age of technology, and that creates new avenues for discrimination and inequality."

An Amazon Web Services spokesperson said the company required customers to be legally compliant and "responsible" — customers may be suspended if they abuse its services.

"Our quality of life would be much worse today if we outlawed new technology because some people could choose to abuse the technology," she said.

"Imagine if customers couldn't buy a computer because it was possible to use that computer for illegal purposes?"

Amazon did not respond to further questions.