I came by this great post Are You Delusional??? on RecruitingBlogs.com , so I decided to share it right away. The author's thoughts on how people use LinkedIn apply to everyone, not only recruiting professionals.
Most of us send invites, respond to the ones sent to us and assume that we are building a network. The reality is that all we do is only creating an electronic list of people we know or knew in the past. The whole point is to utilize that network by actually communicating with our contacts. LinkedIn is a tool facilitating the networking, not the replacement for it.