The CommonCraft video "Social Networking in Plain English" very clearly demonstrated how networks get things done and show how people are linked. Finding friends, finding partners, making connections is a function of social networks like Facebook, MySpace and LinkedIn. These connections, which are hidden in the real world, are clearly visible in social networks online.
The Facebook tutorial marked was short and clear. I saw that there were many others so I watched them as well. All short, clear and precise to learn how to use Facebook.
I registered for Facebook, looked for friends to add, and invited them to "friend" me. (I chose several of the 23 things participants from my region.) I completed a profile (rounding up a picture wasn't easy), joined a 23 things group (mostly southern MN people), and was able to write on a wall there. I will check occasionally in the next week to see what transpires. I found many library patrons from the public library in my hometown, but most of them were children when I knew them. They are now young adults and scattered widely about the world.
I also explored MySpace, but didn't join. I mean, how many of these things can you handle without sucking up all your time? But I might go back later just to see how many connections it would find if I did.
Personally, I like the businesslike, no frills, approach of LinkedIn for professional contacts. People can find you (and I have - when seeking hard to find material so I can ask the author - with very favorable results) and if you want to, you can keep in contact via e-mail, or IM, or other means without all the extra kind of social page upkeep. Call it networking without the social component. The author of the article "Twelve ways to use Facebook Professionally" said that she by adding these people (from LinkedIn) to Facebook feels more connected to them without having to actively maintain a conversation via email and can look for business opportunities out of shared interests. I suppose there is something to that but it's mostly in your perception.