After several years of work with our customers I decided to summarize my experience by gathering the most common user confusions resulted in questions to our technical support service. I think that most of these issues were caused by wrong ideas or interpretations people may have had. In other words, in each specific case the problem was caused not by the lack of information, but rather by some sort of incorrect assumptions.
Of course, nothing like that would be possible if everyone spent couple hours reading the user guide before trying to use the product. But for some reason people rarely do it this way.