Shami is studying how people decide which experts to contact. He found that people typically look for experts who involve themselves in social activities related to their areas of expertise--for example, those who contribute to discussion forums or maintain a related blog. Shami believes that such activities are a reliable sign that an expert is willing to participate in a wider community, especially since it takes effort to maintain a high level of participation in these activities.

Shami believes that searching expertise should include some social data, yielding as top results experts who are not only knowledgeable but also approachable. Eventually, it could also be possible to feed information about users' interactions with experts back into the system to further improve results.

Peter Pirolli at the Palo Alto Research Center, who studies Web searching behavior, says that analyzing social networks can also reveal another type of expert: one who is good at carrying information from one specialized group to another. The ability to carry information between specialized groups can be crucial to innovation, and may be something that companies want to look for when hiring, Pirolli says. He suggests that this type of expert could be found by analyzing social networks and looking for people with strong ties to members of two distinct expert clusters.

Wulf stresses that any method designed to identify expertise must pay attention to how much data mining users will accept, particularly if it is to be built into a commercial system (as Wulf's colleagues are doing with a startup called C3 Networking). In testing his system, Wulf says that users often worried about the consequences of exposing information about their own knowledge. Some bosses feared that competitors could use the information to hire experts away from their company; some workers worried that fellow employees might overwhelm them with requests for help.

Companies using recommendation systems need to think about how to manage the social situations that will result from the system, says Wulf: "We make things visible that were not visible before, for the good and for the bad."