Read
this article.
I find it really hillarious.
"If we had something to hide, we wouldn't have met with them in the first place..."
If the bush & cheney wouldn't have met with them, then everyone would've think that they have something to hide, which would be much worse.
"Bush said it was important for him and Cheney to appear together so that commission members could 'see our body language... how we work together.' "
yep... how they 'work together...' get it? wink...wink... nudge...nudge... 
Anyway, the commission is ".. is chartered to prepare a full and complete account of the circumstances surrounding the September 11, 2001 terrorist attacks..." I don't think how well the Pres and it's VP work together is relevant. If they work well together, the general public would see it in their actions, especially when someone doesn't work well with bush. If they have nothing to hide, they shouldn't mind talking to the commission alone should they?
If they have nothing to hide, they shouldn't mind getting recorded, especially since they weren't under oath. Plus the final report from the commission will have to go through the white house anyway, so why worry about it?