critical mass

critical mass n.  In physics, the minimum amount of
   fissionable material required to sustain a chain reaction.  Of a
   software product, describes a condition of the software such that
   fixing one bug introduces one plus {epsilon} bugs.  (This malady
   has many causes: {creeping featurism}, ports to too many
   disparate environments, poor initial design, etc.)  When software
   achieves critical mass, it can never be fixed; it can only be
   discarded and rewritten.