i believe that the ripe ncc tried this allocation idea initially,
but discovered that the ncc ended up with bits of address space
here and there which was just not the right size, so the ncc
would end up allocating more non-contiguous space anyway.
with that experience the ncc has abandoned that practice.
perhaps, daniel, geert-jan or someone else from the ripe ncc
could speak about their experience.
--elise