I work in User Experience/Customer Relations at NetSecure Technologies. In that capacity, one of my major tasks has been to prepare and execute support materials. A security product is useless if customers cannot or will not use it, so teaching people how to use the product is especially important.
Psychologists have argued (quite effectively) that different people employ different learning styles. Personally, I learn best when I can read something - give me a book and I can become an expert fairly quickly (strangely, I have much more difficulty absorbing information if I read it online). Other people learn best when they can hear something. And still other people learn best when they can actually try something out. Customer support is about supporting people the way they need to be supported - there is no room for ego, and no room for, "well, this works for me" thinking. So, I have tried to employ as many different learning styles as possible in all of my support materials.