We have just submitted a paper to the Special Interest Group on Information Retrieval (SIGIR), "Mining Trail Logs To Determine the Visibility Of Navigational Hubs in Search Results."
The paper makes some very interesting reading! I don't want to give away the findings but we are very excited about the results.
The paper comes out of our collaboration with academia over the past year. If you're an academic who is interested in 'search trails' please contact us. There's much more research to be done!