There are two big issues: the disgusting journalistic techniques of the tabloid press, and Murdoch's stifling control of the media (analysed with gloom by none other than Charles Moore in his piece this morning, "I'm starting to think that the Left might actually be right").
The closure of the News of the World solves neither problem. It deprives Murdoch of some of his share of the overall media scene, but he remains dominant; and while of course it is good that he has been prevented from expanding his satellite TV holdings further, that actually is not a defeat, it is a potential victory which may have been only deferred rather than thwarted. Any response short of dismantling Murdoch's control of the media is a failure.
As for the hacking itself, the NotW was unfortunate in that they got caught, but they were certainly not the only guilty newspaper and equally certainly not the worst - it's pretty obvious from any reasonable analysis of the UK media scene that the NotW is far exceeded in malevolence and gutter journalism by the Daily Mail. Any fix to this situation that does not have the Daily Mail (and the others) screaming is a failure.
One part of the answer became clear to me in the fuss over superinjunctions a few months ago. As a non-UK resident I had no qualms whatever about researching the details of some of the superinjunctions. And I came away thinking that in fact all the ones I could find details on were entirely reasonable; the injustice was that these measures were available only to the rich, and not also to the average person subjected to tabloid abuse. There is no public interest in revealing anyone's sex life, rich or poor, as far as I can see. Any response which does not give privacy rights to all citizens is a failure.
What chance of success? You tell me.