One of the weakest links in it security are the users. This is very important as in a company, managers and employees are the first that can compromise your network.
Bad surfing habits, using the network resources in unwanted and unaccepted ways are some of the issues that a network administrator can handle. Unfortunately social engineering is not one of the issues that can be addressed directly.
This article is to give an overview of this issue to the people that are supposed to cover the overall network security of a company:
http://www.windowsecurity.com/whitepapers/Social-Engineering-The-Weakest-Link.html
Also Social Engineering event targets as Google,Apple and Microsoft with fun results: http://www.zdnetasia.com/social-engineering-for-fun-and-profit-62202279.htm