i don't think facebook will be out of the game anywhere soon.
where i'm from facebook is barely used for it's original purpose, but much more as a news-feed or a login-method for countless mobile games, shops, etc. That alone is enough for facebook not to cease, i think :)
That's a very good point.
One of the main reasons I have kept my Facebook account is for it's other uses.
However, I am talking about Facebook profitability, and that comes mostly from having active users who give them data and viewers for advertising.
Remember, social networks are all about momentum and critical mass. If they are found to have helped the Russians, how many people will boycott and move elsewhere?