Social networking is all the rage in recruiting these days. Hearing or reading about some of the claims being made — that soon sourcing will become extinct as social networks begin to interact, for example, or that we are close to finding the “ultimate solution” as some would have us believe — one could be forgiven for thinking that soon recruiters will be able to just tap social networks for all their talent needs.

The buzz around social networking is reminiscent of the claims made by weight-loss products. While there are some success stories, these tend to be the exception. There is not a standard template that can be used to replicate success. There are some approaches that hold promise, but a reality check is necessary to separate the hype from what’s practical.

The premise of social networking — that by getting connected to a group, a recruiter or an employer can tap into a vast pool of talent — seems logical, but it’s not quite that simple. One common fallacy is that social networks are an easy way to connect with groups of similar individuals — software engineers likely have lots of friends who are similarly employed. But there’s little evidence to support this line of thinking. There’s a lot of academic research on social networks, and what it shows is that people join online social networks 1) to primarily support pre-existing social relations, and 2) to build social capital. Research shows that a person’s network predominantly reflects factors like ethnicity, age, religion, and sexual orientation. A person’s professional interests are very low on this list; even peoples’ attitude toward children ranks higher.

Research at Michigan State University established that the single biggest motivation for people to establish or join online social networks is to maintain offline networks — that is, stay connected with people who are already their friends or with whom they have some offline relationship. That doesn’t preclude similar professionals, but those are a minority of a person’s connections. This is reinforced by evidence from Korea — the population of which is among the heaviest Internet users in the world — that some 85% of people claim that they use online social networks primarily for the maintenance and reinforcement of pre-existing social networks. There’s no reason to believe it would be any different elsewhere.

The other reason people join social networks is to build social capital — broadly referred to as the resources accumulated through the relationships among people. For individuals, social capital allows a person to draw on resources from other members of the networks to which they belong. These resources can take the form of useful information, personal relationships, or the capacity to organize groups. Access to individuals outside one’s close circle provides benefits such as employment connections. Social capital is also related to an individual’s psychological well-being, such as self-esteem and satisfaction with life.

The size of any individual’s network is also far smaller than what it may appear to be. Research by Facebook shows that the while the average number of “friends” in a Facebook network is 120, the number of people on an individual’s friend list with whom they frequently interact is much smaller. An average man responds to the postings of only seven of those friends by leaving comments on the posting individual’s photos, status messages or “wall.” An average woman is slightly more sociable, responding to 10. When it comes to two-way communication such as e-mails or chats, the average man interacts with only four people and the average woman with six. For people with larger networks such as 500 friends, men leave comments for 17 friends and communicate with 10, women for 26 and communicate with 16. The smaller numbers largely represent the offline networks and the source of their social capital. So what about the hundred plus other “friends”? Lee Rainie, director of The Pew Internet & American Life Project that has done much research into social networks, has an explanation: members of online social networks are not so much “networking” as they are “broadcasting their lives to an outer tier of acquaintances.”