@kimschulz What do you use instead? What's App? Skype? I use these too but usually Skype for scheduling meetings/interviews and What's App for texting friends instead of SMS. I use FB too, but mostly to send links etc I use Viber exclusively for my family.
I used Viber almost everyday. It has changed how I stay in touch with my family in Australia. The connection quality can sometimes be poor but considering I can chat to my parents and sister for free, it's a great service. I don't like constant notifications for stickers but that's my one major gripe.