I use LinkedIn for business and Facebook for personal (I maintain a corporate page at Facebook but use it far more for personal stuff especially since emigrating). LinkedIn has brought me work and contacts, and is a good showcase for presentations and references, Facebook is just a lot of fun and a great way to keep in touch with friends you dont see regularly.
Twitter, I also operate a corporate account and have an app that cross posts whatever I put as my personal message on LinkedIn as a tweet… but to be honest I don’t feel I’ve truly got to grips with Twitter at all, the constant stream of info just seems like a bit of a mess and hard to filter and make sense of. I think its good for spotting trends and searching for recent stuff on topics of interest, but you quickly end up following a whole bunch of people some of whom prolifically blurt out so much content, I don’t find it that useful so far. Could be just that I don’t truly ‘get’ it yet though.
And wise words from Jurdy, whatever you post to any of these places, consider to be in the public domain for eternity, however much they try to make you feel in control with privacy settings etc,
Mx