At last year's social computing symposium, one of the participants (alas, I can't remember who...but I think it was Elan Lee) suggested that we try an interesting exercise. It's not exactly a "circle" of trust...more like a square. But it was great fun, nonetheless.
I didn't realize that Ponzi Pirillo had captured it on video and put it on YouTube, until my older son's best friend found it and showed it to him.
I highly recommend trying this yourself. It seems impossible that it would work, but it does!