networking site,” because it isn’t about social relationships. Rather, it is concerned mainly with business and professional relationships.

One useful feature is just helping keep track of how to get in touch with people you know—if they didn’t tell you their new email address, you can still reach them via LinkedIn. (Disclaimer: I have been using LinkedIn for a while, but only as a regular member.)

But LinkedIn goes further: It provides ways to use the network, not just the direct links. Bob Metcalfe, co-inventor of Ethernet, described this effect in what is now known as “Metcalfe’s Law”: The value of a communications network is proportional to the square of the number of nodes. LinkedIn provides tools that let you send a message to someone indirectly, by using a chain of links in the network. For example, if you’re looking for a job at company X, you can search LinkedIn for someone at the company, perhaps in the division or group you’re interested in. You might not know anyone there, but maybe it turns out that you know someone who does. Perhaps there’s a longer chain that gets there. Using the network, you can send a message that can be forwarded along the chain, with each link going between people who do know each other. Sometimes, people may decline to forward the message. But the overall value is much greater than what you get from the people you link to directly.

An interesting question about all of these is: How many do you need?

That is, what is the value in belonging to different social networking sites (using the term in the broad sense)? This isn’t very clear now.

From an individual’s point of view, each new site is new overhead—another profile to fill out, another place to upload your

email address book, photos, and so on. The question is whether or not there’s enough value there compared to other sites you’re on. Recently, I’ve been getting more invi-

tations to different professional networking sites. Do they add anything to what I already have? The main value seems to be that they are used by some people who have my email address in their address book, and it’s a useful link to have. But with only a few, it doesn’t seem compelling. With a lot, it might be.

These different approaches to “social networking” suggest that more is going on here than is captured by a single term. In many cases, what is missing is context, or the more complex structure of real social networks. I’d venture to guess that the structure of social networks for (say) college students is simpler than the structure of social networks for people who have been working for a while, have professional relationships, and a wider range of personal interactions.

For example, consider a working parent, who has been out of college for about 15 years. He or she is part of many “social networks” in the non-technical sense, such as current colleagues, colleagues from previous jobs, friends from college, a high school reunion class, a college reunion class, other parents on the kids’ soccer teams, other parents in the kids’ classes, volunteer organizations, and so on. There’s probably some overlap in those networks, but a page on MySpace doesn’t begin to capture the distinctions in that network at all. Indeed, as more people who know each other socially join a more network-structured site such as LinkedIn, the distinctions can get blurred.

What we’ve seen is that the combination of capabilities on sites like MySpace or Facebook, such as messaging, keeping in touch, sharing photos and videos, and so on, are a powerful set of tools for many kinds of groups. Making it possible for those groups to come together, whether for a soccer season or a lifetime, is an interesting and innovative~use _{of the Internet. We should see more of it.}

 

DOI: 10.1145/1346942.1346946

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