I am HUGE proponent of LinkedIn. My opinion is ANY business person (tech guy, sales guy, magazine editors, IHs, Sr. Execs) is crazy to not be using LinkedIn. I am not so sure about the impact of Facebook on safety and health brands yet — I’m playing with that now.
LinkedIn lets one really build his personal brand. I use LinkedIn as an online enhanced resume. Instead of me telling you "I am really in the loop at Grainger," if we are connected you can scroll through my connections and see all the sr. execs I am connected with on LinkedIn.