WhatsApp killer feature was “No paying for SMS ever, just your data bills”, which was much lower than SMS fees in many many countries, which also explains the popularity of WhatsApp outside of the USA and in many Asian countries.
And it was tied to your phone number instead of a login ID, so anyone with a WhatsApp sign up could interact anyone else who had it, instead of having to find your contacts again like with a new IM service.
WhatsApp killer feature was “No paying for SMS ever, just your data bills”, which was much lower than SMS fees in many many countries, which also explains the popularity of WhatsApp outside of the USA and in many Asian countries.
And it was tied to your phone number instead of a login ID, so anyone with a WhatsApp sign up could interact anyone else who had it, instead of having to find your contacts again like with a new IM service.