My department has a Twitter account, that I have access to. It's for posting departmental news but if there is really something to read on Twitter that wouldn't otherwise be accessible, I guess I could use that. I don't think that's gonna happen.
FB is for work for me. Colleagues and members of work groups are spread all over the world. Institutions, conference calls and updates from my university I went to grad school to, also in there. My Cat Rescue, so I know if there is an emergency and someone can't do their shift, things like that.
In the end, it's really all about how you use