Having the role at CXO level SHOULD be a reminder to the entire company that it's important.
However, I kind of assume she was never treated as an equal with CTO, COO and CFO - which might explain her leaving.
In reality, this should probably be a lower level position with some sort of built-in escape valve where they had an internal channel directly to the board in case they were overturned on something they felt was important - but I don't really understand Apple corporate structure.
Also: Here in Europe, one of the reasons Apple sells so well is that they put a lot of stock in the privacy of their users.
Remember that it's part of EU law that our data should never touch American servers*, because you guys keep looking at it!
*: REALLY complicated topic REALLY simplified and exaggerated for effect.
Edit: Heh, I originally wrote "privacy of their products" by mistake, which is really more true of the pre-iPhone Apple