When Stephen Scheeler became Facebook's Australia chief in the early 2010s, he was a true believer in the power of the internet, and social media, for public good. It would herald a new era of global connection and democratise learning. It would let users build their own public squares without the traditional gatekeepers. There was that heady optimism phase when I first joined and I think a lot of the world shared that, he told the BBC. But by the time he left the firm in 2017, seeds of doubt about its work had been planted, and they've since bloomed. There's lots of good things about these platforms, but there's just too much bad stuff, he surmises. That's no longer an uncommon view as scrutiny of the largest social media companies has increased around the globe. A lot of it has centred on teenagers, who have emerged as a lucrative market for incredibly wealthy global firms - at the expense of their mental health and well-being, according to critics. Various governments, from the state of Utah to the European Union, have been experimenting with limiting children's use of social media. But the most radical step so far is set to unfold in Australia – a ban for under-16s that has left tech companies scrambling. Many of the social media firms affected have spent a year loudly protesting the new law, which requires them to take 'reasonable steps' to keep underage users from having accounts on their platforms. They have claimed this ban actually risks making children less safe, argued it impinges on their rights, and repeatedly pointed to the questions around the tech that will be used to enforce the policy. Australia is engaged in blanket censorship that will make its youth less informed, less connected, and less equipped to navigate the spaces they will be expected to understand as adults, said Paul Taske from NetChoice, a trade group representing several big tech companies. The worry inside the industry is that Australia's ban - the first of its kind - may inspire other countries. It could become a proof of concept that gains traction around the world, says Nate Fast, a professor at the University of Southern California's Marshall School of Business. In recent years, multiple whistleblowers and lawsuits have claimed that social media firms are prioritising profits over user safety. In January, a landmark trial will begin in the US hearing allegations that several – including Meta, TikTok, Snapchat, and YouTube – have designed their apps to be addictive and knowingly covered up the harm their platforms cause. All deny this, but Meta founder Mark Zuckerberg and Snap boss Evan Spiegel have been ordered to testify in person. The case consolidates hundreds of claims from parents and school districts and is among the first to advance from a flood of similar lawsuits which allege social media contributes to poor mental health and child exploitation. As Australia's social media ban was considered, then formulated, the firms had little to say publicly. However, behind closed doors, many sought to bend the government's ear, lobbying for alternative solutions that would empower parents rather than enforce a blanket ban.