LinkedIn- Social Networking for Business

As we all battle to find ways to optimize local search results, there is finally some help in the accessability of others with stake in the same mission.
LinkedIn is a three-year-old service that takes your personal business network online. LinkedIn is all about business: recruiting, sales, investment. It's not exactly a marketplace or a job site but rather a community of more than 8 million people who rely on one another to get things done.
After a slow start, the service has nearly doubled its membership during the past year. Seeded with Hoffman's own high-powered network, a magnet for tech's movers and shakers, LinkedIn has capitalized on the Web 2.0 boom to attract more dealmaking members and race past its rivals. "If every professional had a profile on LinkedIn, you could find jobs, references, experts, old classmates, whatever you needed to do your work. Think about how rational that is."
The mechanism at LinkedIn that overcame that obstacle is very simple: Anyone can join, but to make someone else a part of your network, you have to invite them and they have to accept. And whom would you rather invite to your network, someone who ranks below you in the work world or above? "You are more likely to invite up than down for your own network," says Guericke, LinkedIn's marketing VP. "That's only natural, but what that does is keep the quality high on LinkedIn.
Unlike other networking sites' advertising-driven model that puts them on the treadmill of attracting ever more users, LinkedIn also makes money from services. People - mainly the site's 60,000 recruiters - pay an average of $3,600 a year for premium features such as sending messages to LinkedIn members outside their own networks.

The new free services include LinkedIn Answers, in which you can post a question for other experts in your area to reply. My extremely local search savvy boss and mentor took full adavantage of this service and you can read his local search inquiry and answers