Furthermore, wear debris particles that are generated can interfere with the reading and writing of diskettes. The biggest external threats to magnetic media are strong magnetic fields from commonplace sources such as unshielded loudspeakers, computer monitors, windshield wiper motors, refrigerator doors, etc. These require near contact to effect immediate damage. However, even placement within a few inches can gradually degrade an unshielded disk or tape. Even in a pristine environment, magnetic media have a shelf life.
Tapes are liable to magnetic print-through.
All media, but especially tapes, are liable to the unavoidable chemical breakdown of long molecules and larger particles. The formulations that allow higher storage densities involve complex substrates, binders, particles, and lubricants. Complexity feeds entropy. Ample research and experience provide evidence of what can go wrong with magnetic media as a result of binder degradation, magnetic particle instabilities, and substrate deformation. Optical media are susceptible to damage from high humidity, rapid and extreme temperature fluctuations, and contamination from airborne particulate matter.