I've been using LinkedIn for a few months now. I think it's like anything else - if you devote some time to it, it will pay off. I've been working on building up my network, and I just spend a few minutes, a few times a week on it. I can definitely see it being a tool to get business - if done properly.
I think the whole idea is, not so much that you will solicit people in your firends' networks, but that the more people you have in your network, the more you will show up and be seen by everyone in their network. It's a slower, more seed-sowing type of thing.
Plus, linkedin has some other nice tools like asking and answering questions, which can also get your profile seen. In my name field, I don't just have my name showing, but also what i do - I think that can help as well.
just my $.02