I saw the light when I realized that Simon Peyton Jones (of Haskell/GHC fame) purposely used Comic Sans in all of his presentations -- just to weed out who was paying attention to the styling over the content. Generally, I think this might be a good principle, but you can definitely take it too far. For example, SPJ's slides are always well-articulated and don't contain L33tsp33k (or whatever we call what the kids use on IM these days).