I never was particularly good at navigating human social networks, so what makes all you social networking lemmings think that someone like me is going to do any better just because I'm on Facebook or LinkedIn? To paraphrase R.B.Fuller, the most important thing about me is that I'm an average, ordinary human being. So even to my friends, I'm virtually invisible.
There is a vanishingly small probability that any one of you social types will ever see my posts, let alone bother to read through them, let alone be able to make out the words with more than two syllables. I can't help it that the working memories of social networkers are limited to fewer than 60 characters... most of us ordinary humans still think in terms of narratives, like the "sentences" and "paragraphs" we learned when pencils were still made from trees.
As an experiment, try placing a "salt" text somewhere on your Facebook profile. I used "A TREE FALLS IN THE FOREST", and added an instruction to anyone who saw it to post it to my wall. In the whole year, one person took the bait. So for all intents and purposes, the time I put into filling in information on Facebook is wasted. Ditto for this blog. I'm invisible. Virtually no one will read it. On the other hand, Facebook gets real monetary value from me filling out all that demographic information for them, and I get nothing out of it myself.
So here's my thesis: social networking tools are not additive but multiplicative. If you're already skilled at the art of making friends and holding together social relationships, social networking will multiply your reach. If, like me, you can be absent from an event and have everyone swear you were there; you speak loudly yet people right in front of you consistently fail to register your voice; or you remember most acquaintances with clarity but they haven't the foggiest idea of who you are; then your multiplier is somewhere between 0 and 1 exclusive. The fact that everyone knows your profile sits out there, comfortably ignorable, renders us even more invisible.
As a corollary to this hypothesis, I conjecture that were I not even using a social networking tool, I would have at least stuck out by virtue of my absence. This is based on my long experience having my speech ignored: I learned that lowering my volume was much more effective at gaining the attention of those around me, than was raising it. I remember family telling me that my problem was I spoke too softly; in fact it was just such a feint which gave them this impression.
The real bottom line is this: after a couple of years of use, I'm not feeling, seeing, or obtaining any material benefit from using social networking services. I see no particular reason why I should expect anything different by continuing to do the same thing. So the natural conclusion is that I should stop, and divert my attention elsewhere.