Soon after becoming a mother, Tanya O'Carroll noticed something very strange. Every time she went on Facebook, she was bombarded with advertisements for baby products. How, she wondered, did these companies know that she was a potential customer? She tried to stop the ads by changing her Facebook settings - but they just kept coming.

O'Carroll decided to find out exactly how much Facebook knew about her - and was horrified. Altogether, it had tagged her with over 700 characteristics.

It knew where she liked to go on holiday, what kind of clothes she bought and what type of films she enjoyed. It also knew about some far more personal subjects, such as her health, politics and family relationships.

Social-media users, the Times noted in a leading article, "are under greater anonymous surveillance than they could ever have imagined, even in a dictatorship".

O'Carroll is now suing Facebook's parent company, Meta, for the right to opt out of the profiling which is used to sell ads. The case could cost Meta - and other social media companies - a huge amount of money. If they are not allowed to collect so much information, their profiling will be less accurate - so businesses will be less keen to advertise with them.

This is not the first legal challenge Meta has faced. In June, the US Department of Justice forced it to stop using algorithmsAny set of rules followed by a computer. In the context of social media, "the algorithm" refers to the intelligent AI that learns the interests of the user and presents them with posts that it thinks will interest them. which meant that some people were not shown housing ads because of their race, sex or age. In September, the Irish government fined Instagram €405m (£351m) for failing to protect children's data properly - particularly their phone numbers and email addresses.

In most countries you need to be at least 13 to have a Facebook account. But research in the US¹ found that 32% of children aged 7 to 9 used social media, and around 50% of children aged 10 to 12.

In Britain, the government has set up a Digital Markets Unit to stop tech companies abusing their power. Along with the European CommissionThe executive body of the EU, responsible for suggesting new EU laws and overseeing their implementation. , it is investigating whether Facebook is guilty of this.

Asked why she did not simply close her Facebook account, O'Carroll said: "It is just not something that people feel that they can leave - and even if they wanted to, where do they go? Because it's a monopoly."

Yes: Our privacy is constantly being undermined, both by tech companies and by governments. Without proper protection, we could all find ourselves living in police states under constant surveillance.

No: Wealthy people and companies already use lawyers to intimidate anyone who wants to expose their wrongdoings. A right to privacy would allow them to do that even more frequently. 

Or... It is a nice idea, but it would be very difficult to define what a right to privacy should cover. And some people live in such crowded conditions that it would be impossible to assert that right.

Algorithms - Any set of rules followed by a computer. In the context of social media, "the algorithm" refers to the intelligent AI that learns the interests of the user and presents them with posts that it thinks will interest them.

European Commission - The executive body of the EU, responsible for suggesting new EU laws and overseeing their implementation.