The use cases are not to outline the structure of the wiki directly, they are so that we can get into the mindset of a new user... One of the problems with becoming a specialist is that you forget what is actually common knowledge. One of the problems with "hanging out" in a social network like this for too long is it starts to serve new and strange purposes... that can only evolve with time...
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yes, I'm guilty of using mobileRead as a mild stimulant while sleep deprived, and as an antidepressant when I'm feeling lonely... 
)
Forums are a good way to document a dialog, and have everyone get a chance to speak up... but they are harder to get that immediate satisfaction a first time browser might want/need to get hooked... and Its all about sharing the addiction!
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The use case of "looking for materials we have problems with" is a perfect example of the sort of thing I need to realize but overlooked... If we can address this request, change their expectations in a friendly and prompt manner, we might yield a more pleasant encounter with those miscreants.
In fact, it has been my experience that when expectations are not met, that is what causes distress... not the experience itself.