That's pretty sad. The worst part is they just mentioned that they sped up the homepage by 75%, which is really irrelevant for a site that isn't technically focused like Google. They're trying to appeal to the wrong crowd.
A 400ms improvement in page load time at Yahoo directly increased page views by 12%
Although Digg isn't actually speeding up their page serving, you should note that page speed is one of the cornerstones of conversion rate optimization.
Google will even penalize slower sites in SEO rankings. Page speed is about the easiest way to improve engagement and conversion rate with modern CDNs etc:
http://www.webperformancetoday.com/2010/07/01/the-best-graph...
http://conversionvoodoo.com/blog/2010/04/official-google-new...