The Next LinkedIn
jmlite.tumblr.com
jmlite.tumblr.com
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.
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 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.