I don't really think that the adds ban and the rumors of Facebook launching a coin are related. I think banning crypto adds was a good decision, because most of those adds were of ICOs that would most likely end up in scams. This move will slow down the speed at which these companies spread. I actually think that this measure could also be taken by google, both on their adds and maybe YouTube channels. Those youtubers that helped promote bitconnect for example, are as guilty as the company itself in my opinion. Preventing scams to spread will be good in the long term for crypto markets.

As for facebook coin, I don't know if they will launch it or not. If they do, it will be the end of steem in my opinion.