It would be a nice feature to free or reallocate an instance of DirectBuffer.
APIs like jogl and lwjgl are using DirectBuffers to hold 3D graphic data. You waste a lot of unused memory because the DirectBuffer is only freed at the end of a VM run. When you need a smaller or bigger one you can't free or reallocate the old DirectBuffer. You have no possibility to scale the memory usage of the application if you use DirectBuffers.