Social networks raise some fascinating questions, and perhaps offer some clues about how we will be reaching out to each other in future.
Rheingold's interest in online social networking began 25 years ago
The virtual world of Second Life is a highly sophisticated online social network where around 400,000 users play out their lives in thousands of acres of digital space.
Second Life offers unprecedented levels of interaction between its users. For example, budding and established musicians are using the game's audio-streaming features to play "live" concerts on stages made of polygons.
There is a thriving economy too. Many players make real-world money out of businesses they have set up in Second Life, which may include designing virtual clothes or owning a casino.
If you are still not convinced of the business case for online social networks, Google recently shelled out $900m (£481m) to provide the search engine and adverts for MySpace.
Each week seems to bring a new variation on the theme.
This week saw the launch of Weblo, a new concept which aims to provide a carbon copy of the real world by allowing members to buy, manage and trade virtual assets as diverse as celebrities and landmarks, making real money all the while.
For every new idea, there are dozens of people queuing up to tell us they came up with it first. Social networking online is no different.
We think we have tracked down a man who really was instrumental in creating online social networking: Howard Rheingold.
Spencer: So just give us an idea of your background in the area. Why are you held in so much reverence?
Howard Rheingold: I'm somebody who seems to stumble into things 10 or 20 years before the rest of the world does.
So about 25 years ago I became very excited about the prospect of people using computers and networks that communicate with each other. I called it 'Virtual Community'.
I knew then, that networks do something that the rest of life doesn't. It enables you to connect with and communicate with people you don't know or didn't know before, but with whom you may have something in common.
Spencer: So let's come right up to date now. We have seen MySpace go for over $500m (£268m), Rupert Murdoch and his company bought that, and people were saying that's a crazy amount to pay for what is essentially a teen social networking site.
Now we see Google coming along giving Murdoch his money back and then some in one fell swoop. Are we going to see Google being able to make back their money?
Howard Rheingold: I think it has to do with a very major shift in the way cultural products and fashion are sold.
It used to be the broadcast method. Magazines, television, radio and cinema were how you broadcast advertisements and then people bought things en masse.
Now we are seeing the young people in particular in these social networks selling things to each other, even creating the things that they are selling to each other and of course, there is a lot more potential in millions of people selling things to millions of people, rather than a few people selling things to millions of people.
You know Andy Warhol said 'in the future that everyone will be famous for 15 minutes', a blogger by the name of David Weinberger said 'in the future everyone will be famous for 15 people', and I think that what we are seeing now is the technology is giving us a vast middle ground between the amateur whose parents are the only ones interested in their productions and the professional in which you have megastars.
You now have many, many bloggers making not a huge amount of money, but the beginning of a decent living through ads they put on their blogs.
So I think that instead of having five super-groups that make billions, we may see hundreds of thousands of garage bands that have their few hundred fans that are able to keep them alive.
Spencer: So in the future, are we all going to be locking ourselves away and only interacting with people online?
Howard Rheingold: Well in the future, if we are going to have a whole load of people on this planet we are going to want to have them staying in their apartments a little bit more.
Spencer: (Laughs) Well, that's your own opinion.
Howard Rheingold: Well there is never going to be a substitute for face-to-face communication, but we have seen since the alphabet, to the telephone and now the internet, that whenever people find a new way to communicate they will flock to it.
Certainly what the internet enables for you to find people that you have something in common with, that you might not have had some way of communicating with before and they might even be on the other side of the world.