According to the policy that’s to be implemented by February, all of Whatsapp’s data would be shared with Facebook (and basically advertisers or buyers).
Data can very easily fall into the hands of, or be sold to, potentially harmful entities.
Everything seemed to be going smooth.
There’s no money stream for the developers.
Of course Whatsapp has always shared data with Facebook.
But they’ve now taken out the option they provided users to ‘opt out’ of sharing their data.But they probably didn’t expect people, to retaliate this hard.