Damn. It's just not simple enough yet. The stocks and flows discussion was too hard. People still find the idea of anticipating and answering questions before the "asker" has the occasion to ask incredible (as in not credible).

So I'm thinking that perhaps we can use the fact that it happens all the time -- though goes unnoticed -- to make it clear.

How about this...

Try to recall a time when you were fully engaged in some task for at least one hour. For that hour you didn't have to search the internet, or any other reference. Ask yourself why that was possible. Ignoring the possibility that you were channeling some other legitimately smart person, the answer is that already knew what you needed to know to get that job done during that hour. You had sourced the information prior to needing it from friends, books, TV, magazines, hallway conversations, or possibly you deduced it from principles you'd learned (that you picked up from books, teachers, whatever).

In every case, you sourced the information from somewhere, and then made it a part of your personal toolkit, to be applied whenever needed. You only need a reference, you only need to search, when your sources fail to properly prepare you.

Social networking, social filtering, is all about using a social network to do a better job sourcing -- a much better job. Because your ideal social network consists of people very similar to you, the social filtering provides what must be the most relevant, most highly targeted, selection of sources. Who or what can know better what you need to know, than people just like you that have already been where you're going. (Clearly, if you're always on the cutting edge, your trailblazing tendencies have a price. For 99 percent of us that's not an issue.)

Professional social networks share the burden of identifying the best sources. It's as simple as that, but the difference it makes is hard to underestimate. Understanding it changes the way we support community, measure community, and interact with the communities we serve.