I think online networks are great. They allow me access to a large number of people and information which otherwise would be off bounds - not easy to go for a quick drink after work when childcare is always an issue. However, there is so much information and people to follow/read about that I tend to find it rather paralysing.
I have a facebook account which I use sporadically, mainly for personal purposes.
My LinkedIn account tends to get more attention, it's where I get many of the professional updates. It was through linkedin that I'm now connected to Webjunction and Social Media, a subgroup of Webjunction. Updates come to me via email which means I can easily check them. It was through them that I attended my first Webinar "Trends in Library Training and Learning"
Having an American based webinar in the UK meant that it took place after working hours. However, it turned out to be a bit of an ordeal as real world and the virtual one collided - partner and children on one side side and the seminar on the other. The seminar itself wasn't easy to follow - there was the speaker's voice coming out of the speakers, the presentation at the centre of the screen and the attendees/participants tapping away on the right-hand corner of the screen. Next time I must make sure to find a corner in the shed. Not yet quite sure how to deal with the interesting but constant stream of comments.
I've just signed up to LISNPN and found in it quite a lot of great stuff such as the downloads pages and blogs by Ned Potter, thewikiman. I also have now CILIP in my group of networks.
I haven't done much of the participation bit yet but hope to do it soon - too shy? too slow? maybe, but haven't given up yet.