As an experienced candidate in search of the right assignment - you cannot overlook the Social Networking sites that are mushrooming everywhere. Though it may sound silly to be a part of group responding to invites from unkowns - one never knows which link might work.
The truth is that one need not be present in every social Networking site. But , some prescence is a must just to spread the word around.
If you find your job to be prefect and really dont feel the need for looking out then you can give this whole Networking thing a pass. But, if you are seriously looking at furthering your career or for whatever reason then You cannot miss out on this.
I have collected some links here that speak about the impact that social networking is having on recruitment.
Frank Langfitt talks about how professional recruiters are taking to Soc Net sites to reach candidates.
Guest Blogger blogs about Web 2.izing your job search.