In 2014, Facebook acquired WhatsApp Messenger for $19 billion. At that time we only thought Facebook purchased the popular messenger to benefit from the service fees. But, Facebook made the app completely free. Yesterday, Facebook announced that WhatsApp will soon start sharing data with Facebook. Well, probably this was the intention of the acquisition from the very beginning.
There is not much to worry as Facebook is only getting the information from WhatsApp to bring you more targeted ads, which is a monetization strategy for the messaging app, which is free and features no ads.
WhatsApp will remain free of banner ads, but will share your phone number with Facebook so that businesses can reach you easily. For instance, an Air Line may reach you to inform you of a delayed flight and a bank may contact you to notify you of fraudulent transactions in your bank account.
WhatsApp assures that your information will not be sold to any business or advertiser. Also, no one will be in a position to read your messages as the end-to-end encryption still remains. However, if you are still not comfortable with the new feature there are ways to stop it.