Great for global travelers: Mobile messaging apps overtaking text messages

WhatsAp is one of Silicon Valley's most buzzed-about companies, yet it actively avoids the spotlight, operating out of a small office in Mountain View, Calif., with no sign on the building entrance or on the office door. Unlike most start-ups eager for media attention, WhatsApp Inc. says it doesn't want or need it. Its popular mobile messaging app has spread so quickly by word of mouth that in just four years it has amassed hundreds of millions of users who collectively send as many as 18 billion messages a day. WhatsApp belongs to a new generation of messaging services that are revolutionizing 20-year-old text messaging technology and escalating the mobile messaging wars. "In many countries, consumers have decided they prefer these mobile messaging apps," said Tero Kuittinen, an analyst with mobile diagnostics firm Alekstra. Now they are taking the U.S. by storm. That's particularly worrisome to wireless carriers that have already lost billions in revenue from customers s