Circle of Trust [d3.do] by São Paulo-based D3 shows the potential asymmetry of your social network at Google Plus. In other words, the organic network diagram highlights how your social network is divided between the people that are inside the so-called "circle of trust" (people that you trust, and they trust you), and those who are somehow outside.
Green dots represent the people that have been 'circled' and reciprocally have circled you back. Yellow dots represent those persons that were sufficiently important for you to have been circled, but they have not bothered to circle you back. Lastly, red dots map to people that have circled you, but you did not care to circle back.
Not surprisingly, Mark Zuckerberg's diagram is extremely red, though Britney Spears' is quite yellow. What this actually means for the personality of those people, is up to you.
More detailed information is available here.