Facebook’s 'like' button is ubiquitous across the web. It’s how user data is collected, meaning adverts and newsfeeds can be targeted more effectively. Some say there’s nothing to worry about, but others point to the Cambridge Analytica scandal, suggesting how Facebook might shape our opinions. But is there something else we should be worried about? Approval from our friends and family can be addictive – so is the pursuit of “likes” on social media the reason we’re glued to our mobile phones? Tim Harford asks how should we manage our compulsions in this brave new online world.