That some OS's next version of their disk utility will not merely be able to erase your disk but also write out zeros to it.
Oh, but most do that, I hear you say.
But this one I'm told will actually go back and do it 7 times over and even 30 times over. Just in the absolutely paranoid case you perceived that someone might be able to detect the aura of your erased data.
So many zeros... Like pieces of popcorn dropped on the floor of a theatre.
I feel secure now :)