http://thinkprogress.org/2008/09/14/cheney-wiretapping/
So Cheney's Cheney, David Addington, hid info about wiretapping from White House Chief of Staff Andy Card.
Why?
Well since Cheney's legal status as part of the Executive branch has been put into "doubt" solely by Cheney's saying, "I know you are but what am I?" and the reason for this is that such a claim allows the administration to make the FURTHER claim that such memos and other records within Cheney's office are therefore exempt from the Presidential Records Act, and critically -- further examination by other parties who might find this or that ILLEGAL.
Indeed, Cheney's records were about to be destroyed by him, and a formal injunction from the court had to be obtained, obliging him to retain those records until a Constitutional judgment can be made as to his status. Which that other case was up in the air, Cheney had intended to just go ahead and break out with the old Ollie North shredder.
I would submit that everyone in the White house knew about this illegal shit, but the really incriminating stuff has been shuffled off to other places, like the RNC email servers and "lost".
Cheney, having basically started his career in the Ford "damage control" Administration, is using every loophole he can think of to avoid prosecution.