Just reread your blog post. I wonder if the answer is not about being careful simply with the people you choose to bring in your network. Maybe it's too hard: you choose to trust your immediate connections, but what about their connections? Is the friend of my friend my friend too?
You see that question on social sites where you can choose how far you wish to share your "privacy". Friends? Friends of friends? Everyone?
Another way is perhaps to have a dedicated setup, like the dedicated pizza boxes that google rent to customers. I know a guy who does something like that, he's got something offering a panel of functionalities similar to linkedin, but I don't know if that would correspond to what you're looking for.
Discussed your article with a friend of mine. People join LinkedIn to initially build an online resume which advanced into LinkedIn selling data or became a hangout spot for sales rep or HR - thus there is so much spam content.
Let's say tomorrow you are to make a quality linking connections platform. Why would people join it? What incentive would people have to join yours when they can still do it on LinkedIn, even if LinkedIn is horrendous?
It is quite difficult in the beginning when you have to differentiate yourself from LinkedIn while convincing others to join and build your community.
I like to hear more of your thoughts on this issue - I think its quite fascinating to think about "how to build a new LinkedIn?".
I think the best way to start may be to ignore LinkedIn. I agree with everything you say about LinkedIn. It's the playground for sales reps, recruiters and HR people. And in that it does play a valuable role. Yet buried way back in time was this idea that you might connect to someone new through an existing mutual connection. There was trust based on that connection that made it a "warm" introduction. That concept is all but lost today.
I think you convince people to join specifically because they believe the only folks contacting them via this service will be trusted, warm and valuable. They won't get a lot of unsolicited requests from people who don't offer a mutually valuable relationship.
Another way is perhaps to have a dedicated setup, like the dedicated pizza boxes that google rent to customers. I know a guy who does something like that, he's got something offering a panel of functionalities similar to linkedin, but I don't know if that would correspond to what you're looking for.