I don't think any social media will replace a search engine, facebook tweeter and the rest might be heaven for marketing and for people selling their products.
I know for a fact that most IT professions say google is their number one tool, if they see an error or a missing library they google it to see what/where to get it. The people making the libraries or documentation about program/operating system errors won't ever open up a facebook or tweeter page (I'm talking about open source projects).
They have no PR teams and to them its also a waste of time, lets take this site for example its a lot eaiser for google to scrape it and broadcast our information then for us to write articles here and also a mini article on facebook. For one Bigguy isn't a fan of it and I'm against it as well
As for the other Admins and mods I don't know if any of they have the time or patients to log in here look at the posts then, log into facebook and look at the comments on the same article.
This is just my opinion we will see what happens.