If their coin is not on a blockchain, it's dead in the water. It WILL be hacked, and as soon as that happens, people will leave in droves. Zuckerberg must know how risky that is.

If their coin is on a blockchain, but people don't get paid to post and curate, Steem still has a huge advantage.

If they do pay to post and curate, but post text is not stored on the blockchain, then they still have censorship, and Steem still has at least that advantage.

If their blockchain doesn't allow other apps to connect and monetize their content, Steem has the advantage.

If they do allow other apps, and they censor content, they are going to piss off the app developers and they will leave.

And as soon as they start censoring content with which there is money involved, people will leave.

The only way I can see for them to do this right and is to develop something similar to Steem.

If that happens, they will have an open source, censorship free platform where anyone can post about how Facebook just copied Steem. And by that time, the price of Steem should be high enough that we can entice a good number of users to switch over.