What Makes Messaging Different?

Line, the Asia-based instant messaging app, says it has reached 100 million downloads in 18 months.  That sort of raises the issue of how over the top instant messaging apps are different from text messaging. 

In many cases, instant messaging is a relatively straight forward substitute for text messaging, the value being that users do not incur incremental costs. WhatsApp and Kik might be examples of that use case. 

But Line seems more akin to chat (broadcast messaging), than text messaging (person to person communications). In other ways, Line seems like a gaming portal, and less like a simple substitute for text messaging. 

But Line also is a bit like a social network as well. 

Line also has become an over-the-top voice calling app. The point is that it isn't so easy these days to describe how "instant messaging" is different from "text messaging."

Text messaging and IM are in many ways substitute products. But sometimes even that distinction is inadequate. Messaging seems to be evolving.