More compelling insights from Kathy Sierra (via Seth Godin) in her blog post "Why marketing should make the user manuals". Heck, you don't even have to read the story, just look at the picture and you'll get the point.
Even stand-outs in the experience management realm mess this up. Just compare the Ikea catalog to their self-assembly instructions. The catalog is appealing, glossy, full of photos, and uses diagrams only when they are actually clearer and better for communicating. The self-assembly instructions are clearly not part of marketing, they are part of low-cost manufacturing.
If you think about how much of your business comes from repeat customers or referral customers, you might want to think about changing your approach.