This article presents pioneering research on measuring virtual wealth in an open virtual world for diagnosing the health of virtual worlds. It proved the existence of an open virtual world by proving the existence of a free choice of virtual currencies for virtual goods between distinct virtual worlds. By discussing the features of open virtual world in a circled networked organization, the article devised a virtual wealth measuring scheme, called Gross Virtual Product (GVP), for any virtual world. Based on this scheme, it suggested an accountability matrix to account for a changing virtual world regarding its total virtual wealth, profitability, user participation and happiness. To demonstrate the suitability of GVP scheme and accountability matrix, the article has conducted a case study on SecondLife. com, which showed the appropriateness of the proposed scheme and matrix. The research made in this article is very important. The proposed measuring scheme and matrix help virtual world participants perceive the possible risks of the participated virtual worlds in advance to make better decisions on virtual business.