Jeff Atwood (aka @codinghorror) gives a great run-down on why performance matters on the StackExchange network.

URL: http://www.codinghorror.com/blog/2011/06/performance-is-a-feature.html

URL: http://www.webperformancetoday.com/2011/07/12/case-study-printingforless-com-proves-that-mortal-companies-are-no-longer-settling-for-fast-enough/