My take is that Facebook is banning crypto ads because it has taken so much heat over the past 12-18 months over "fake news" and "Russian bots" and all that stuff. The people at Facebook have literally been called to Washington in order to testify in front of Congress. (sort of like being called to the principal's office in high school) In the U.S., people are saying that Facebook is bad for democracy. With that kind of heat, I'm sure that Facebook's legal department is looking to minimize any future scandals or points of conflict with regulators and watchdogs. They certainly don't want to be blamed for a "market crash" or millions of people losing money if their cryptocurrency holdings take a dive in value.

So, while I certainly see your point about Facebook trying to co-opt rivals, I still think that Facebook is still too early in the process of crypto and blockchain to ban advertising for that reason. And I'm not sure if Steemit is even on Zuck's radar right now. I think he's thinking mostly in terms of "social commerce" and how to get people buying and selling things via Facebook and Facebook Messenger.

However, when the lightbulb does go on in Facebook HQ, i have no doubt that Zuck will act to co-opt Steemit (or any other perceived rivals) as quickly as he moved to co-opt Instagram, Snapchat and Whatsapp.