Gilbert Direct Marketing posted this very well done presentation on slideshare looking at how LinkedIn lets you network in the 21st century:

In the presentation, they classify users of LinkedIn as casual users or power users and identify ways to help make yourself a power user of the platform. Businesses are increasingly utilizing Linked in to explore career opportunities, find groups and individuals of similar interests, or just expand their network in general. LinkedIn can be a very powerful tool if you decide to use it and this presentation helps you to use it well should you choose. They close with this summary slide: 

That last point is really the most important if you want to realize social media success. One piece of the puzzle will not create the full picture.