This topic got beyond the social media policy talk I gave at today's Capital Communicators Group, but it's a good question -- and in terms of unofficial policy, speaks to the issue of what some clients of mine see as a monolith of social media. Should you, must you, try everything at once? Must you give over your entire schedule to it? Of course not!
My personal (and professional) preferences: I'm active on Facebook, LinkedIn, Blogger and Twitter, and invite people I've met to join me there. For social networking, I find Facebook and Twitter the most facile and useful sites--but if you need a special-audience site, by all means, seek it out. LinkedIn's comfortable for many networkers, but lacks the functionality of other sites.
My advice? Choose a site and start there first, particularly if you are testing the waters for your business. Many of my clients develop pilot projects in social media--there's no need to tackle all the sites right away, at least until you've mastered one to start.
Timewise, social media work is like any other effort. Plan out your schedules to allow time each day and week for social media. Think about what you can replace from your existing array of tasks on social media. Try using social networking sites as internal collaboration sites--there are plenty of private options, from secret Facebook groups you can set up to direct (private) message on Twitter. For me, these are effortless -- and essential -- parts of my day.