Facebook have a lot of users...but I´m not sure that it was the best place to announce an ICO. The best way is to have activity in Reddit, Medium, Twitter, Telegram and specialized forums like this one. We are started to announce our ICO recently and the most of the messages that we are receiving with questions, sugestions or asking more information about us are from Twitter and Reddit users.
Sorry to say but i think that you are wrong, Facebook is the no doubt the best place for ICO advertisement. Facebook has too many users almost from everywhere in the world, therefore it is really contributing too much to advertise different ICOs. I can hope that it will continue introducing ICOs in future.