16. The computer-readable memory device of claim 15 , where the one or more instructions to compare the first set of context data with the second set of context data include one or more instructions to determine a proportion of categories that are common to both the first list of categories and the second list of categories.
16. The computer-readable memory device of claim 15 , where the one or more instructions to compare the first set of context data with the second set of context data include one or more instructions to determine a proportion of categories that are common to both the first list of categories and the second list of categories. 17. The computer-readable memory device of claim 16 , further comprising one or more instructions to weigh the categories based on relevance scores associated with the categories.