Facebook look pretty useless to me , I mean the same audience that you are likely going to target is the same one that is here . I know that It's possible to target other users but they probably won't be as much as interested as the ones coming from faucets , bitcointalk or other btc services where their main objective is to make profit after the ICO.
Usually I do not trust any money related things if I come across anything other than this forum. I am ready to spend $100 for an ICO, if someone is suggesting here but definitely I will not listen to my Facebook friends for similar thing.
Facebook may have different type of audience, but advertising here for a crypto currency based services must be right approach.