You're making that assuming from a US viewpoint. In Germany every kid in school is on WhatsApp, as my teacher friends tell me. The same is probably valid for other markets.
In The Netherlands everyone is on WhatsApp, and instead of sending a text message or something like that, it is common to hear "Ik zal even een appje sturen" (I will sent you an WhatsApp message), or "Ik app je wel" (I'll WhatsApp you).
But, to be honest, I think this is a horrible move. Make clear that WP will move more in the direction to become more Social. I have thousands of contacts saved that I have no intention of having any social interaction that is not straightforward. My mechanic, the person who cuts my hair, my gardener, a girl I met yesterday, the person I sold my car to. With all these, I interacted using Whats app. But with none of them, I want to share what I share with my friends, my relatives etc.
My facebook is frozen exactly because of this. WP, especially its groups, was a territory of segregated interaction, this was spectacular. Facebook inc could kill this by including functions like that.
I remember when MSN, Skype, and others message programs have tried put a feed inside their app. They failed.
