Denis O’Brien: Digicel made him a billionaire.  Photograph: Dara Mac Dónaill

Denis O’Brien is well known in business and media circles for taking a rather muscular approach to his opponents and critics. He may need to beef up a(...)

Viber Media chief executive Talmon Marco (right) speaks next to chairman and chief executive of e-commerce operator Rakuten Inc Hiroshi Mikitani during a news conference in Tokyo today. Photograph: Yuya Shino/Reuters

Japanese e-commerce giant Rakuten Inc has said it will buy call and messaging app provider Viber Media Ltd for $900 million (€657 million), aim(...)