It doesn't require registration headache.
This service is currently available for iPhone only. I am waiting to have new version for my Android :)
You don't have to register! You know your phone number, and so do your friends, so why bother with yet another username and password? Viber uses your phone number as your "identity" and lets you make free Viber phone calls to any of your friends that have Viber - using THEIR phone number.
visit the original site : www.viber.com
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