We’re introducing Page publishing authorization starting with people who manage a Page with a large audience in the US.
Facebook can and will use the phone number as a personal identifier with which to track one’s activities outside of Facebook. I did not give Facebook my phone number because I know they use that to cross link your account to third party data.
Have you ever used a store loyalty card? All of those are associated with your phone number and are used by retailers to track all of your purchases. That information, in turn, is sold to third party data aggregators, such as Axciom, who in turn re-sell the collection of data to others. The data is used, presumably, to target marketing efforts. The phone number is the key identifier used to link together your online (Facebook, Twitter, ad networks) with your offline retail purchase history.
I run a software programming page that likely falls into the category of requiring this new verification. That page is the primary reason I did not delete my Facebook account, but instead dropped out of about 65 groups, unfollowed all other Pages and removed about 1/4 of my “friends.