Marti Hearst, a professor at the School of Information at the University of California, Berkeley, says that Surf Canyon succeeds in presenting the reordered links in a clear, useful, and unobtrusive way. It doesn't require people to do any extra work, as does Google's WikiSearch, a feature that lets users personalize their results by voting them up or down.

However, in her test cases, Hearst found that the algorithm's re-ranked results weren't completely useful. "Where personalization works is where queries are ambiguous," she says, but queries have become increasingly longer over the years, and they tend to provide clues that help the engine disambiguate the results on its own. Additionally, in Hearst's tests of Surf Canyon, she found that it only untangled the different meanings of the acronym ACL (which could mean both anterior cruciate ligament and Association for Computational Linguistics) to a certain point: it kept including mixed results even when she felt that her clicking choices had made it clear that she was interested in the linguistics group.

Cramer and his team say that they have gotten more positive results. In a study they performed, some participants saw a second page of search results that were reordered according to Surf Canyon's algorithm, while others saw a second page with standard results. The researchers found that the participants who had access to reordered results clicked on them 30 to 40 percent more frequently.