Silicon Valley is a uniquely American creation, the product of an entrepreneurial spirit and no-holds-barred capitalism that now drives many aspects of modern life.
But the likes of Facebook, Google and Apple are increasingly facing an uncomfortable truth: it is Europe's culture of tougher oversight of companies, not America's laissez-faire attitude, which could soon rule their industry as governments seek to combat fake news and prevent extremists from using the internet to fan the flames of hatred.
While the US has largely relied on market forces to regulate content in a country where free speech is revered, European officials have shown they are willing to act. Germany recently passed a law imposing fines of up to 50 million euros ($59 million) on websites that don't remove hate speech within 24 hours. British Prime Minister Theresa May wants companies to take down extremist material within two hours. And across the EU, Google has for years been obliged to remove search results if there is a legitimate complaint about the content's veracity or relevance.
"I anticipate the EU will be where many of these issues get played out," said Sarah T. Roberts, a professor of information studies at UCLA who has studied efforts to monitor and vet internet content. Objectionable content "is the biggest problem going forward. It's no longer acceptable for the firms to say that they can't do anything about it."
How closely to manage the massive amounts of content on the internet has become a pressing question in the US since it was revealed that Russian agencies took out thousands of ads on social media during the presidential campaign, reaching some 10 million people on Facebook alone.
That comes on top of the existing concerns about preventing extremist attacks. This month, three men were arrested after allegedly using smartphone messaging apps to plot attacks on the New York City subway and Times Square from their homes in Canada, Pakistan and the Philippines. The plot was thwarted by an undercover officer, not technology.
In some ways it goes to a question of identity. Social media companies see themselves not as publishers but as platforms for other people to share information, and have traditionally been cautious about taking down material.
But the pressure is on to act. Facebook, Google, Twitter and YouTube in June created the Global Internet Forum to Combat Terrorism, which says it is committed to developing new content detection technology, helping smaller companies combat extremism and promoting "counter-speech," content meant to blunt the impact of extremist material.
Proponents of counter-speech argue that rather than trying to take down every Islamic State group post, internet companies and governments should do more to promote content that actively refutes extremist propaganda. This approach will unmask the extremist message of hate and violence in the "marketplace of ideas," they argue, though critics see it as just another form of propaganda.
Facebook has recently published details of its counterterrorism strategy for the first time. These include using artificial intelligence to prevent extremist images and videos from being uploaded and algorithms to find and disable accounts linked to pages known to support extremist movements. The company also plans to increase the staff dedicated to reviewing complaints of objectionable material by more than 60 percent to some 8,000 worldwide.
"We want Facebook to be a hostile place for terrorists," Monika Bickert, director of global policy management, and Brian Fishman, counterterrorism policy manager, said in a statement. "The challenge for online communities is the same as it is for real world communities - to get better at spotting the early signals before it's too late."
But Roberts argues the companies have been slow to react and are trying to play catch up.
The fact is the technology needed to detect and remove dangerous posts hasn't kept up with the threat, experts say. Removing such material still requires judgment, and artificial intelligence is not yet good enough to determine the difference, for example, between an article about the so-called Islamic State and posts from the group itself.
In other words, taking down much of this material still needs human input, said Frank Pasquale, an expert in information law and changing technology at the University of Maryland. Acknowledging that is difficult for companies that were built by pushing the boundaries of technology.
"They don't like to admit how primitive their technologies are; it defeats their whole narrative that they can save the world," Pasquale said. "You kill off the golden goose if you cast doubt over the power of their algorithms."
Employing enough people to fill in where the algorithms leave off would be a massive task given the volume of material posted on social media sites every day. Just imagine trying to moderate every puppy photo or birthday greeting, said Siva Vaidhyanathan, director of the Center for Media and Citizenship at the University of Virginia.
He believes that moderating content is ultimately impossible because you can't create a system that works for everyone from Saudi Arabia to Sweden.
"The problem is the very idea of the social media system - it is ungovernable," he said. "Facebook is designed as if we are nice to each other. And we're not."
The US government response has been more focused on policing than regulation, with security services authorized to sweep up huge amounts of electronic data to help them identify violent extremists and thwart attacks. Beyond that, authorities have mostly relied on the market to drive change amid fears that heavy-handed regulation could interfere with the First Amendment rights of law-abiding citizens to speak out and exchange information.
European courts have had no such qualms, balancing freedom of expression against the right to privacy and community cohesion.
For example, the European Court of Justice in 2014 ruled that people have the "right to be forgotten," permitting them to demand removal of personal data from search results when they can prove there's no compelling reason for it to remain. As far back as 2000, a French court ordered Yahoo to prevent French internet users from buying Nazi memorabilia on its sites.
The European Union's executive has been most active in matters of antitrust. This year it leveled a huge 2.4 billion euro ($2.8 billion) fine on Google and ordered it to change the way it does business, for example how it shows search results.
"There's a real cultural divide," said Edward Tenner, author of the upcoming book "The Efficiency Paradox: What Big Data Can't Do." ''European governments have been more committed to incorporating the ideas of social justice and the Americans have been much more on the libertarian side."
