judith meskill's knowledge notes...

"Chatting people up at networking events is of limited value, but obtaining introductions is the key to getting the ear of the people they want to reach," Konstantin Guericke, co-founder of LinkedIn, told CNN. "People join because they believe the most valuable new business contacts come through referrals from people they already know and trust."

LinkedIn and others like Ryze and ItsNotWhatYouKnow are the business equivalents of the popular Web site Friendster. Most are free to join, profiles have no photos and your list of contacts is called your "tribe."

LinkedIn, active in 80 countries with 48,000 regular users, does not allow people to cold-call each other. Instead mutual contacts can vet whether they want to refer you. "We facilitate over 1,000 successful referrals per month. Our users accept three-quarters of all requests because they never hear from strangers," says Guericke. "Users only request a referral for a specific business or career purpose. It's not something 'extra' they work on, but a more efficient way of doing what they already do."

These sites say they make finding business leads quicker and more reliable, including hiring employees, signing up distributors and locating industry experts. A downside is that for a successful new contact, both parties must feel the other side has something to offer. If you do not have a valuable network to start with it is unlikely that others will refer you or ask you to be part of their network. And there is already a debate on how these Web sites will make money.