LinkedIn is a social networking site designed specifically for the business community. The goal of the site is to allow registered members to establish and document networks of people they know and trust professionally.
A LinkedIn member’s profile page, which emphasizes employment history and education, has professional network news feeds and a limited number of customizable modules. Basic membership for LinkedIn is free. Network members are called “connections.” Unlike other free social networking sites like Facebook or Twitter, LinkedIn requires connections to have a pre-existing relationship.
With basic membership, a member can only establish connections with someone he has worked with, knows professionally (online or offline) or has gone to school with. Connections up to three degrees away (see six degrees of separation) are seen as part of the member's network, but the member is not allowed to contact them through LinkedIn without an introduction. Premium subscriptions can be purchased to provide members with better access to contacts in the LinkedIn database.
LinkedIn was co-founded by Reid Hoffman, a former Executive Vice President in charge of business and corporate development for PayPal. The site, which was launched in May 2003, currently has over 300 million members from 200 countries, representing 170 industries. According to Reid Hoffman, 27% of LinkedIn subscribers are recruiters.