I had a pleasant little fort carved out for myself adjacent to a magma pipe that reached the surface. This was a populous fortress, and it soon became my custom to dump any unwanted immigrants into the exposed lava to dispose of them with minimal fuss.
However, it was also my custom to have a large store-room (well, catacombs) full of coffins to be used for burials when appropriate. Now, every time I would dump dwarves into the magma, a coffin would be assigned, if available, for all of them. Despite the fact that falling into the magma burned away their clothes, corpse, bones, and so on. Their body was fully destroyed by the magma, yet they still got a coffin.
This was bad enough, as it ate through the coffins I had reserved to minimize unhappiness in the event of accidents or siege casualties.
However, I soon realized that if I didn't have any free coffins, these dead dwarves would form up a sort of queue. Whenever I build more coffins and allowed them to be used for burial, no matter how much time had elapsed, the nonexistant bodies would immediately take priority and "fill" the coffins up until all of said dead dwarves had been "buried" in the coffins. Thus, I could have a single recently dead dwarf waiting for a burial, and a full catacomb. I would build 10 coffins and designate them for burial, and the dwarf would not be buried because the coffins were instantly filled, upon becoming available, by the immigrants I killed a season or more prior who were in this ghastly nominal queue to be "buried" in them.
This problem could easily compound itself such that if a player did that for a while before starting to give dwarves proper available coffins that they would either have to build a coffin for every destroyed dwarf that had ever been to the fortress, or avoid coffins entirely and be forced to let resident dwarves rot in the graveyard.
Suggestions might obviously be that "filling" a coffin requires that a job is completed by a dwarf wherein they haul reachable body parts to the coffin, and foregoing the burial if there are no parts to be entombed. Maybe this would require friends/family to have unhappy thoughts about the dwarf dying a terrible death that prevented a burial.