<p>SEOUL, South Korea -- A handful of smartphone apps that began as basic instant-messaging services have amassed several hundred million users in Asia in just a couple of years, mounting a challenge to the popularity of online hangouts such as Facebook as they branch into games, e-commerce, celebrity news and other areas.</p><p>Among them is Line, which has grown to 60 million users, mostly in Asia including at least 29 million in Japan. Its developer estimates the number of users will reach 100 million by the end of this year. Also popular is Kakao Talk with 60 million users, more than half in South Korea where it originates. Other successful messengers are Nimbuzz made by an India-based firm which has amassed 100 million users including 31 million in Asia, and WeChat by China-based Tencent, which is nearing 200 million users.</p><p>The rapid growth of such applications underlines that people are increasingly going online using mobile phones and other wireless devices. It is a trend that has proved problematic for the world's most popular social networking site. Facebook has lost more than $50 billion of its market value since its initial public offering largely due to doubts about its ability to successfully insert advertising into the mobile version that a large and growing number of its 955 million users access from smartphones.</p><p>"Japan, Korea and to a lesser extent China are leading the way in terms of mobile messaging-centric apps that move into diverse and potentially very profitable new service areas like gaming, affiliate marketing, next-generation emoticons," said analyst Mark Ranson at research firm Ovum. "Offering a free, high quality messaging service is a good way of building a large and loyal user base which can later be introduced to more readily monetizeable services."</p><p><a href="http://www.mercurynews.com/business/ci_21574216/instant-messaging-services-explode-asia-challenge-facebook-and">Keep reading...</a></p>