SAN FRANCISCO, June 17  Ian Clarke was a 23-year-old computer scientist living in Scotland in 2000 when he started a global controversy by deploying an online system called Freenet. The system was intended to make it possible to share information anonymously, and to make it virtually impossible to remove from the Internet once it was placed there.

Since then he has moved to the United States, gone back to Europe and returned to the United States, in the process starting three venture capital-backed companies. But he has not given up on his original goal: to engender democracy by making it simple to share accurate information.

Mr. Clarke’s latest project, a Web site called Thoof, is an attempt to improve on sites like Digg and Reddit, where communities of users filter and rank links to news articles and blog entries. Thoof began operating on Friday in invitation-only mode and is set to open to the public next week.

Mr. Clarke is obsessed with the fact that even when accurate information exists on the Internet, it often does not have the political impact that it should.