Post-It Notes on Shabbat

Question

Dear Rabbi Abadi, I would like your opinion on the permissibility of using (both placing and removing) a Post-It note on Shabbat (for instance, to mark a spot in a book, or to leave a pre-written note for someone, or to cover a light switch). I've heard two different answers: 1) Why would it be assur? 2) How could it be mutar? How would it be different from any other gluing of one thing to another? Kol Tuv, David