nothing stop facebook to come with a coin in 2018.
This kind of giant doesn't go down like this, and anyway ppl are not client of facebook they get there for free, so the panic will come when the advertisement industry start to drop they are the real clients not ppl wrong signal to watch here.
Don't get me wrong I'd love to see facebook go down the tube. Steemit need a private message for members to start competing with websites like facebook. Hopefully steemit team will move to EOS blockchain by 2019.