Comment 2 for bug 1187372

Those machines will become destroyable once the units on them are all removed; working as currently intended. Should this behaviour be changed to allow machine destruction to induce unit destruction (and, indeed, destruction of all containers and contained units, etc)?

That seems slightly drastic; but perhaps it's no worse than destroy-service destroying all relations automatically. However, it is somewhat complex to implement that behaviour cleanly, and it's unlikely to be a very high priority soon; will the workaround described above suffice for the time being?