The larger and more complex the subject matter, the harder it is to develop meaningful learning experiences. Without a clear idea of the big picture there's a risk of concentrating too heavily on some learning points while skipping others entirely. It becomes easy to get lost in the information wilderness. More pertinent still is that when you're dealing with complicated or technical topics there's a very real risk of misinterpretation (or just plain getting it wrong), particularly if you as the designer are not well versed in the subject at hand.

Imagine a roomful of bored-looking people forced to listen to a presenter while he reads a list of dot-points to us from each of one-hundred-and-nineteen slides. It's about time someone threw in a lifeline. Or a grenade.

Training material should be slick and to the point. Slides should be used to support what the presenter says, not the other way around. They should be visually appealing, light on text, and certainly few in total number. A handout need not just be those same slides in printed form but modified so it makes sense when read by itself. Pretty basic stuff, huh?