At least you can opt out of some upcoming targeted advertising, though.
Even though Whatsapp recently started offering end-to-end encryption for its users (though not turned on by default) this latest move shows that if you care about privacy, using any app owned by Facebook means you won’t get that privacy.
Most people think that’s not a problem since they don’t (currently) live in repressive regimes, but if you do live in one, you should look elsewhere for your secure communications.
Source: WhatsApp Will Share Your Phone Number With Facebook – Vocativ