Facebook isn’t inherently assur. If you use it for inappropriate things then you are using it to facilitate an aveirah.To put in perspective weddings and grocery stores aren’t assur either. BUT, if you use them to facilitate doing aveiros then maybe you shouldn’t go.You have to have seichel.
Smoking is inherently assur. You are endangering your life and those of the people around you (except according to the one poster who will claim 2nd hand smoke doesn’t exist-which isnt true, but I’ll preempt that comment) Besides the fact that I think no one has mentioned which is how expensive a habit it is. For guys either in Yeshiva or Kollel to be spending their parents, in-laws,and or wives money (@ the rate of $7-$12 a pack)is a . wrong and b.not being very moser nefesh for Torah if you ask me.