I have to admit I had never heard of history sniffing before reading this story. Makes me doubly glad I use Chrome for my browser.
From the link:
“Nobody knew if anyone on the Internet was using history sniffing to get at users’ private browsing history. What we were able to show is that the answer is yes,” said UC San Diego computer science professor Hovav Shacham.
History sniffing can be used by website owners to learn which competitor sites visitors have or have not been to. History sniffing can also be deployed by advertising companies looking to build user profiles, or by online criminals collecting information for future phishing attacks. Learning what banking site you visit, for example, suggests which fake banking page to serve up during a phishing attack aimed at collecting your bank account login information.