He sacks an aide, no great loss to him, but the MP the aide is married to is untouched, so his power base in the Commons is undiminished and the MP appears to be clean.
There you go, Cameron has just shown himself to be just as immoral and unmoved by all this as any of the other troughers.
Vote Tory and nothing will change.
Update: My mistake, obviously MacKay is an MP, but the point is still that surely both of them should go.
Update 2: Post in haste, repent at leisure! Right, what is happening is that MacKay is resigning as Cameron's aide, not as an MP. In other words, all he is doing is getting the idea in front of the public that someone from the Tories has been sacked or made to resign. MacKay is not doing anything here but allowing Cameron to look like he's doing something when he's really doing fuck all.