We have sharing built in (on the 2nd page) but it is not incentivized, yet. We're almost done building in the incentives for it (offering extra entries).
FB: "You must not incentivize users to use (or gate content behind the use of) Facebook social channels, or imply that an incentive is directly tied to the use of our channels."
"c. You must not incentivize users to Like any Page other than your own site or application, and any incentive you provide must be available to new and existing users who Like your Page."
Not entirely dismissive of it, at least! Likes are ok.