Also just about any software that handles business workflow. A common tradeoff in development is dynamic vs efficiency. For example, in a database, if you can define columns for properties you know about, you will have a much faster database than if you created a bunch of "Thing" tables with "ThingProperty" relationships.

  PATIENT
  =======
  PatientId
  FirstName
  LastName
  
  vs

  THING
  =====
  Id
  ThingTypeId
  
  THINGPROPERTY
  =============
  ThingPropertyId
  ThingId
  PropertyName
  PropertyValue

Storing it doesn't take too much of a noticeable hit, but any queries on "Thing" tables get expensive real fast.