Remember, LinkedIn is a professional tool for solving tasks. It is not a cold calling list or directory of your target clients. It IS a first place to check for current and future contacts and business, due to the high quality of the data when it is present. Since each profile is about an individual, automatic self-interest is generated for being well-represented on the web.
An Interview with Martin Brossman on Using Linkedin as a Job Hunting tool. Also see other resources below.