BOSTON--(BUSINESS WIRE)--Viber, one of the world’s leading messaging apps, today announced plans to dial up its marketing efforts in the U.S. as part of its strategy to build and retain a highly engaged audience across the globe. Growing rapidly, with 600 million unique users worldwide, Viber is experiencing high adoption levels in the U.S. and has decided to focus on and invest in this important market. As a core part of the local strategy, Viber has appointed Scott Nelson as Head of Viber Nor