You keep roping in other properties into this, if you want to do that, use their parent company name. 4b users on facebook as in Facebook seems a bit of a reach to me at this point. 4b on all properties, ya maybe. Either way, while I could see it having a negative impact, it would mostly be as an advertising platform, and the net positive of that going away might bring it to neutral.

I know it's imused in some places as their primary messaging service or something, but it seems likely they're not doing much unique here.

So what is this harm you speak of?