The comparison between different scoring schemes (Table ) highlights differences between judgment-based and calculated scores. One of the reasons for differences is data incompleteness, for example where affinity data is only for the presumed primary target thereby precluding selectivity assessment. Even the experimental probes included 195 compounds without bioactivity data. In addition, we found 142 compounds annotated against single targets without selectivity data. The union of these represent 36% of the experimental probes that cannot thus be properly scored. Another reason for differences arises between stringent criteria-based evaluation and expert judgment.