I have noticed recently that reports are dramatically off depending on who runs them. One person runs a sales report and get 10,000 units sold and another person runs the identical report and gets that 7,000 units were sold- because person 1 did not have rights to credit memos, for example.  Yet, no error or warning that anything is amiss- just different numbers.

In another scenario, if a custom field was set that a person does not have access to, the searches are totally disregarding it but still running. So if I had a field of "omit" on a record, and the criteria was does not = omit, and the person doesn't have the rights to view the omit field, the report still runs but it includes omits. In fact, if they look at the search criteria, they dont even see the criteria of omit at all- even though in every other view of the report it is there.