[JOfferijns]

I can definitely confirm this, at least in The Netherlands literally everybody uses Whatsapp and it has slowly become a verb - "I'll whatsapp you the details!".

It's far from the best messaging app, but definitely the most popular (in Europe).

[soneca]

In Brazil here, my girlfriend literally bought a new phone, a low-budget android, just to talk with her best friends through Whatsapp.

[bosky101]

India too...( where whatsapp adoption spread virally from blackberry, symbian, etc first and smartphones later)

i work on an im client[1], and my mom sent me a link about whatsapp :)

[1] to be fair, verbs.im is a gtalk/aol/yahoo multi-protocol client. infact, one day we could wrap over whatsapp as well. not exactly re-building a new graph but re-using your existing lists.