This is powerful, Broderick says, because it prevents dishonest people from artificially bolstering their own ratings with the help of their friends. "Bad actors will become isolated islands of reputation, cut off from the mainland of good people," he says.

Chris Dellarocas, an associate professor of information systems at the University of Maryland, says that public ratings systems sometimes discourage people from saying bad things when they ought to, while anonymous ratings systems cause trouble by failing to hold people accountable when they bad-mouth another person. TrustPlus's model has promise, he says, because people may be more willing to give honest ratings when they know they can control who sees them. However, Dellarocas notes that systems like this work most easily when people are buying and selling, and he's curious to see how well it will work in other contexts, such as when someone is meeting another person via Facebook.

The TrustPlus software released today is only an early test version. But the company plans to launch a full version later this year. Broderick says that he and his colleagues are currently finalizing deals to integrate their system with other companies and to license a people-search feature from an existing site. The company doesn't intend to charge for maintaining users' profiles, and it has no plans to add advertising features. Instead, the team intends to make money by adding support services, such as payment processing and tracking systems, for people who are buying and selling through free online classified sites, much like those offered by the company Channel Advisor, which supports buyers and sellers using eBay.