"[Mr. Khosla] puts a slide on a screen, removes it after five seconds, and then asks the viewer to describe the slide. A dense slide fails the test -- and fails to provide the basic function of any visual: to aid the presentation."
Here's a link to the article: http://www.forbes.com/sites/jerryweissman/2011/10/26/vinod-khoslas-five-second-rule/
I'm going to have to apply this rule to my next presentation to see if my slides can be improved...