The social media giants based in the US may soon face a new attack in Europe: There’s a perception among activists and officials that the basis of their business model – targeted advertising – can be a threat to democracy.

In a speech on June 7, Commissioner Margrethe Vestager – who, as the top European Union antitrust official, has been the nemesis of US tech companies such as Google and Apple – laid out her problems with the way social networking changes people’s political behaviour. One of her complaints is familiar and much-discussed: Facebook and its peers tend to sort people into political and ideological filter bubbles and silos, destroying, as Vestager sees it, the chances of meaningful debate. The other has received less media attention. It concerns political ads and, generally, campaigns’ social messaging.