By doing so, WhatsApp claims that it can more accurately count unique users, better fight spam and abuse, and help Facebook offer better friend suggestions and deliver more relevant ads. To allay fears of privacy intrusion, WhatsApp stresses that nothing users share on its instant messaging service (e.g. messages, photos, account information) will be shared on Facebook or any Facebook family of apps for others to see.
WhatsApp – “But by coordinating more with Facebook, we’ll be able to do things like track basic metrics about how often people use our services and better fight spam on WhatsApp. And by connecting your phone number with Facebook’s systems, Facebook can offer better friend suggestions and show you more relevant ads if you have an account with them. For example, you might see an ad from a company you already work with, rather than one from someone you’ve never heard of. You can learn more, including how to control the use of your data, here.”
With more than one billion active users to date, that’s a lot of user information which WhatsApp is sharing with Facebook and we reckon some users will certainly feel uneasy about it.