Symantec found that the latest Facebook app (since Feb 2013) has been sending your phone number to Facebook's servers without permission on first launch of the app, even if you never sign in and even if you don't have an account.

But let's be reasonable before we get out the pitchforks. If they have your number but no other information because you don't have an account, what value does it have?  It's a credit card without the CV2#. It's a social security number without a name. What you should really be worrying about is the fact that they grab it without your permission when you DO have an account, along with everything else about you.

Details here:

Huffington Post - Facebook has your phone number