Why is every messaging app under the sun trying to sell stickers to you?

This week I rather playfully poked fun at Viber’s introduction of paid-for stickers. That’s because the concept of adding sticker shops has become an industry standard, after the likes of MessageMe, Kik,WeChat, Line, Path, Kakao Talk, Cubie, Maaii, and now Viber, introduced them.It’s becoming a real cliche. Messaging …