I belong to a number of networking sites and have for a while. First I joined Ryze and even went to some of their functions. Then I tried Linked In, but I have not put much effort into it. My latest find is eliyon networking which boasts: Eliyon automatically and continuously grows its base of 15,758,276 people profiles from corporate and personal websites, government filings, press releases and other sources. It is hugely expensive to subscribe, like $10K.
Today Fortune.com posted an article that explores all these various sites and discusses a new breed of networking applications designed for business: "...new companies like Contact Network, Socialtext, and Spoke Software are generating revenues by selling social-networking software to corporations". I recently had lunch with my colleague Cesar Brea who is the new CEO of Contact Network Corporation. He gave me an impressive demo of the product and it clearly demonstrates it's value immediately.
Shrinking the time between making the personal investment in software and getting the valyform is critical to getting people to actually use it. A couple of these companies seem to recognize this. Clearly much as you mention with Eilyon, the amount of insight, access, and influce that you can tap into is a key driver of value. With Spoke's public access growing from 3M to 5M in 2 weeks, you have to think that they are somewhere in the right zone.
Of course part of this investment is the privacy risk..privacy is control.
A couple of these seem to realize this is the core issue. Make control feel like it does in the real world and mimic real world "features" while allowing easy discovery.
In the end, all of these companies are competing against the difficulties of discovery access and information not against each other yet. They are competing against the frustrations of "does anybody know anyone who can help me with.." emails we have all sent.