information:classification, quality:corruption
Arrow's impossibility theorem

Arrow's impossibility theorem is a key result showing that social choice functions based only on ordinal comparisons, rather than cardinal utility, will behave incoherently (unless they are dictatorial). Such systems violate independence of irrelevant alternatives, i.e. they suffer from spoiler effects the system can behave erratically in response to changes in the quality or popularity of one of the options.