Ultimately, a CKO's job should be to fire himself ...
In his weblog Dave Gurteen has an entry on the role of the Chief Knowledge Officer. It relays the popular view that this should be a temporary role to help organizations migrate to a new way of working. I think this is misguided.

The CKO should champion the knowledge-based perspective of the organization and defend it against all the other perspectives that confront managers e.g. financial, legal, marketing etc. A CKO's first job may well be to bring about substantial KM change, but the organization will always be in flux and you need somebody to keep an eye on the intangibles through any subsequent organizational change.

If you get the place just how you want it from a KM point of view you can bet your dog that the next wave of changes due to e.g. legislation will start to undo half of them as an unplanned side-effect. You wouldn't change your accounting practices and then tell the CFO he was no longer needed for 'business as normal' would you?