David Cameron may try to brush away accusations of poor judgement in the light of Andy Coulson's resignation and pretend the whole thing is a nothing story by wishing him well in the future but hoping the story dies down does not make it so.
http://www.bbc.co.uk/news/uk-politics-12251456

At best Coulson was ignorant of what was going on under his stewardship as editor of the News of the World and at worst he was involved in illegal phone hacking, neither of which attribute is to be commended in the Prime Minister's spokesmen. So Cameron has shown poor judgement when he hired someone who was stupid or crooked especially as all this is hardly a recent development and Cameron was well aware of the potential for scandal when he appointed him as Director of Communications.