Online social networks look like glorified dating services, and that's all some are. But they can also be useful for work--from finding a new job to recruiting new customers.

It's trite but true: It's not what you know, it's who you know. You don't get the good jobs by answering want ads; it's your personal connections that get you gigs and customers (and dates, but this column is about technology for the workplace).

Social networks--online systems that connect friends to each other and to friends of friends--seem like they could be highly valuable for business use. A system such as LinkedIn could, for example, direct you to people who could help you in doing your job better or landing a better one.

Maybe you've used a social network and have wondered how to behave on this new medium. Perhaps you've received some social network invitations and don't know what to make of them. (If you haven't yet, you will soon.) How should you handle these new invites? Herewith, a few suggestions for doing business in the new world of social networking.

Rule No. 1: Friends of friends of friends are no friends at all.
It can be awkward enough to be the person in the middle of a requested connection. Say your good friend is looking for a job and wants to connect to another friend of yours, who is hiring. You may love both people as friends, but you may or may not feel good about connecting them for business. When a friend of yours asks you to connect a friend of his or hers to somebody on your network, you're really straining the social fabric. And if the desired connection is between two people you don't know at all--when, for example, you're the third middleman in a five-way link between friends of friends--how can you possibly evaluate whether it makes sense to make the connection?

At this point, you're granting favours for friends on both sides of the equation, but you're pretty much doing it blind, and that puts you in an awkward spot. I never feel comfortable about participating in these multiparty links; I don't think you should put your friends in that awkward position. I'd warn you to simply not make such requests. However, many social networks don't tell you how far away your desired target is, so you can't tell what they're asking you to do. But when it becomes clear that you're are participating in a ridiculously long chain of referrals, it's time to pull the plug.

Rule No. 2: Ignoring someone is actually more polite than saying no.
One of the odd things about a social network is that, if you ignore an invitation to join a person's circle or to make a connection, you can often safely plead ignorance of said invitation.

This is because many social networks build in a mechanism for plausible deniability. If you never respond to an invitation, the instigator may never know it was you who turned it down. If you disregard a request to join a personal circle, it's a little more difficult; you'll have to plead ignorance of the notification you got. Those notices usually come through e-mail, so you can blame your spam filter.

Rule No. 3: People are not trading cards.
Some people like to collect social network contacts they barely know. If such a person invites you to do something, you're then in the awkward position of having to ignore the invitation or turn it down or, by accepting it, adding a bunch of your contacts to the inviter's network.

Beyond the natural human instinct to collect things, gang-adding people to your network has the benefit of extending your circle of friends of friends. But it isn't a savoury habit. You're using people, and it devalues the connections that a social network does such a good job of codifying.

Some social networks, such as Orkut, allow you to specify the type of link between people, from "best friend" to "haven't met." This is a step in the right direction.

Rule No. 4: Guard your friends' trust.
Adding a friend to your social network exposes his or her contact information to the network system you're joining. Most social nets have very strong stated privacy policies, but the act of submitting a friend's e-mail address to a social network can create ill will with the friend. This is especially evident with the contact manager Plaxo, which has a small but vociferous opposition movement. I've met with the CEO of the company and disagree with its critics. But before you attempt to add a buddy to your circle, ask yourself: Would you like it if somebody submitted your e-mail address to a system you didn't know?

Don't get me wrong--despite all of the above, I think social networks are very useful. You can get a job, do business, and find lost friends and contacts, all through these systems. But the novelty of them has led to people going overboard and annoying their contacts. This can have a long-term negative effect: It can turn people off the systems for good. Then when you really need to contact that friend of a friend, you'll get nothing in reply but silence.

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