[QUOTE=wco81;29502364]Do these people live mostly outside the US?

iMessage is really popular on iOS. But WhatsApp has global appeal, especially on cheap Android phones.[/QUOTE

Both! It has served me very well while travelling international, with both Android and IPhone users, to communicate for free. taxis, tour guides, airbnb owners, and even front desk. All free and instant. I have multiple chat groups that friends join, there is even a desktop version.