What is the ruling on the Facebook challenge to donate charity according to the number of likes and comments on a specific post?

If the intention behind the charity is for the post owner to donate the number of likes their post received, then it appears there is no harm in that. However, they are not obligated to give this as charity, because they have not done anything to indicate a commitment to give charity. Publishers must exercise caution when disseminating information and verify its authenticity, especially concerning hadith (definition) and Sunnah (definition), to avoid spreading weak, fabricated, or innovated hadith.