I've never used Viber but years ago a few friends raved about it and told me to download it. As I had unlimited calls and texts, I couldn't see the appeal. However at the time, I didn't have access to either wifi or internet at work and when they installed wifi a couple of years ago, everyone jumped on Whatsapp so we can now send texts/pics etc. I guess it's like Facebook vs Myspace vs Bebo. It just comes down to what is fashionable at the time and everyone runs with it.