I've been experimenting with Facebook. Here's what I've learned so far:
 Scrabulous is addictive. This is an asynchronous version of the board game that you can play with Facebook friends around the world. I'm now having to ration myself on it as a treat for getting my work done.
Applications developers are trying to find addictive applications like this. Most applications don't seem to have this quality. They are something you have a look at once, then uninstall. They seem largely designed for youth, who are amusing themselves by sharing music lists, lists of celebrity likes and dislikes, and similar fluff.
 Seeing status reports on my friends is interesting. I love their sense of humor, which often comes out in these reports. It makes me feel like I know what's up in their lives, even though it's been months since we've had a coffee. But I've also learned that I can inadvertently send messages out to my network that I didn't really want to send to everyone. [Like how addicted to Scrabulous I am.] Or the fact that my book on Innovation is finally coming out in January. I wasn't really intending to make these announcements in this way, but I did anyway.
 It's impossible to manage the circles of relationships effectively right now. My mental map looks like this:
I have an inner circle of friends and colleagues that can have access to pretty much anything there, and already know a lot of it.
Then there's a big second circle that are colleagues or relatives, but not really close. I want to manage the information flow a bit more there. Then there's the big outer circle of people I want to stay in touch with, but are more like acquaintances. Some may be very respected, I may be a big fan, but it would be a stretch to say we are friends. A few on the outer edge are just members of the same organization I am.
And the stripes might separate business from personal.
I suspect others have this issue also, and we need better tools to address this. Right now, the tools lack sophistication. For example, Circle of Friends lets me say how people in my network fit together, but I can only do this publicly. [How rude is that! Guess what, you're in my circle of barely-know-you-and-care-even-less. Bob made my inner circle, but you didn't. Hello!]
 Some people want to be friends with everyone. Today I had a request from Marwan, a 20 year old I have nothing in common with, and no friends in common with. He wouldn't qualify for my outer circle. I'd have to study this phenomenon to understand it, but this sort of thing seems to happen a lot.
I've had sales people try to be my friend on Facebook. Seriously.
 The groups application is incredibly easy to set up, but has limited utility. I have set up two groups so far, and been an administrator on a third, and found the lack of good tools somewhat frustrating. This application could not serve as a work collaboration tool in it's current form. Although it wouldn't take much to fix it.
Clearly, I'm not the only one with these ideas. Because there has been an explosion of applications designed to bring social networking to business people in a more sophisticated way. Most seem to want to build a completely new network. Personally, I don't think that will work very well except for those with deep pockets and fantastic ideas. For one thing, it's largely been tried in existing online communities dedicated to specific topics.
If you are thinking about building a better hot dog stand -- and it seems that many people are -- I would advise you to put your hot-dog stand where there are already a lot of people looking for hot-dogs, instead of trying to get them to walk a few blocks to a new place.
It's a lot easier. It's often cheaper. You won't have to build a completely new platform, you can piggy-back on an existing one.
Consider the challenges faced by competitors to people like Yellow Pages, who are trying to get massive numbers of people over to a different location. This is the challenge you are facing in building completely new networks. If you can be where lots of people already are (just mixing my metaphors a bit), you improve your odds a lot.
Things are pretty fragmented and early stage on the networks thing. But we will see a tremendous amount of development here. It's a good time to be a networker.
I subsequently found a good thought piece on this topic from Suw Charman on the Strange Attractor blog here. Here's one of her thoughts that caught my interest:
My worry is that exposing these hidden networks to the harsh light of the explicit hierarchy could kill them, or vital parts of them. In old-style command-and-control companies, the very fact that you know someone rather senior in another department may rankle with your boss in such a way that they start to work against you, and that would undermine the very fabric of the company. After all, a company isn't a single entity at all, it is a group of people who have social relationships and who need some of those relationships to remain hidden.