Performance and security are like brothers in IT. They are similar and yet they fight each other at times.
Both performance and security are important inherent qualities in IT systems. Who would not want a fast and secured IT system? You want your home computer to be fast and secured. The bank CEO wants his Internet banking system to be fast and secured for his customers.
This was a very nice article on ACE Team Blog. If you wish to read more...Here it is: http://blogs.msdn.com/ace_team/archive/2006/07/03/655524.aspx