Social network software is a hot topic in the US, and has featured heavily in the past two O'Reilly Emerging Technology conferences.
Last year Friendster was the most talked-about service, and it now has more than four million members. That is impressive for a system that is still in beta.
This year, of course, the geek focus had shifted to Orkut, thanks partly to its association with Google. There are now more than a hundred social network sites, including:
These social sites are now moving into the business world. The basic idea goes back to "six degrees of separation", which suggests that if you go via friends of friends-of-a-friend, everyone is connected to everyone else by six steps, on average.
If you know 100 people, and each of them knows 100 more, then you have 10,000 friends-of-friends. Take that a step further to three degrees and you are connected to one million people. At six degrees, the number increases to nine billion.
Sites such as Orkut make the connections easier by giving you a photo and a profile of each person in your network. You can either make contact with friends-of-a-friend directly via the system, or send messages to all your friends-of-a-friend and see if you get any interest. In a few seconds, you can message anything from 50,000 to two million people.
All this has lots of potential, especially if you live in the US and you are interested in dating. Most social network users are young, single and American.
Its relevance to business is another matter.
This kind of system would obviously be extremely useful if you could either create your own walled-off social network on a public system, or run social network software on your intranet. And the software to do this is beginning to emerge.
Enterprise-class social network software needs three things that present web-based systems lack. First, you must be able to verify and authenticate users so that you do not take on board any fakers.
Second, it must have multiple levels of control. For example, you will certainly want to have different access levels for internal staff and external associates.
Third, it must integrate with existing business software. Working with Microsoft Outlook is the minimum requirement, and an ability to work with CRM systems would be highly recommended.
There are at least three companies to watch: Spoke, Visible Path and Zero Degrees.
Social network software is not one of those things that you should be using or even testing today. But I expect it will become important in about five years, and you should certainly add it to your watching brief.
Jack Schofield is computer editor of the Guardian