It's akin to a nuclear exchange. You can only use it once. It's MAD. So you hold onto it to protect a high value asset - your life. Assume that you want charge

It's akin to a nuclear exchange. You can only use it once. It's MAD. So you hold onto it to protect a high value asset - your life. Assume that you want charges dropped unto you - and you get that granted. Then you want something more annoying to the powers you control - maybe that would be granted. But at a certain point the cost to grant you wishes is going to be on the same level as the threat you hold over me, and then I may decide to take the fallout, and be done with it. I suspect we're on the verge of this - Assange has something so damning that the fallout of having him taken out in broad daylight becomes something you contemplate. If this is so, at this point if Assange goes public with what he knows, he's a dead man anyway.