By Gerry Shih SAN FRANCISCO (Reuters) – In recent years, a bevy of messaging apps has fought for global domination, with many boasting a lucrative combination of communications features, online shopping and games. But this week, Facebook CEO Mark Zuckerberg spent a staggering $19 billion to buy WhatsApp, the contender with perhaps the simplest functionality and negligible revenue. WhatsApp, which has 450 million users, has stuck to basic messaging, but also a simple business model of charging users an annual subscription fee of just $1. Zuckerbergs bet may ultimately prove to be a strategic masterstroke: shutting rival Google Inc out of an upstart phenomenon with a unique mobile graph and gaining swathes of users – and their data – in emerging markets.