A few years ago, one of my employers REQUESTED that we all use LinkedIn and we had a contest to see who could get the most connections. I came in SECOND with over 400!! I basically went through my contacts and sent a request to EVERY IT person I knew and then some of the secondary connections. I also joined a dozen groups on LinkedIn.

NOW, I get offers every week because of my LinkedIn profile.

Ironically, this strategy by my company to build social networking caused me to get a very nice job offer (which I took, my current position).

And some companies may not appreciate "hangin out your shingle"... but I always tell every new employer that I am always keeping my options open after an experience of being laid off on the second day of a job that required relocation. I almost always have 2 or 3 active conversations about opportunities. Keeps my resume fresh and forces me to continuously evaluate my career track.

And remember, it is ALWAYS better to be interviewing while you are EMPLOYED...