I have mixed feelings about this. I like WhatsApp because they fixed SMS (by adding group chat and cheaper messaging). I also like the fact that they do one thing and do it really well (ala DropBox).

The client is light and fast. I can use it a dozen times a day and it doesn't get in the way. Skype, et al by contrast are bloated because every new release must add new features. By the time version 20.0 comes out, it's bloated.

Same thing keeps happening over and over again with torrent clients. It happened with WinAmp and to MS Word and nearly every other software that gets popular.

You can almost see the thinking machinery in work. "450 million users? How much are we making per user? $1 per user per year, that's it? Let's get into VoIP, it's a billion trillion dollar per annum industry. Let's get the project managers to layout the roadmap for the next year and set the milestones so we can get there fast."