This is known as the "cheese-cutter effect", as its action is easily compared to the method of cutting cheese with a fine wire.
Sometimes this can occur without an open wound being created, as the fistula stretches in one direction, and tissue fills in behind it.
This is not uncommon with tongue piercings, although the migration usually stops before the jewelry would exit the body.
Contemporary body jewelry is made from surgical grade implant materials, so with proper aftercare during the healing phase and good hygiene, this is rare.
Proper, custom made jewelry can reduce the risk of migration associated with these piercings, although it cannot eliminate it.