A soldier in Afghanistan learned about the death of Osama bin Laden on Facebook. A TV producer got a tip from comedian Kathy Griffin on Twitter. A blues musician received an email alert from The New York Times. And a woman found out as she scrolled through the internet on her smartphone while walking her dog.

Hillary Clinton adopted a sharper tone as she came face-to-face with Barack Obama in a bid to revive her ailing campaign for the Democratic Party’s presidential nomination, but never achieved a “knockout blow”, US political pundits said today.