I think you and bham are wrong on this. The privilege is being asserted as to DOJ documents. Obama asserts executive privilege on Fast and Furious documents - CNN.com
Holder had already asserted it, but it took formal claim to assert it.
I base this in part on my experience as a lawyer in that you can't simply refuse a discovery request based on privilege. You have to affirmatively assert it, say why, and that is done so as to make the issue ripe for a court to decide.
It appears that is what has happened here. Although the headline is that Obama has asserted it, that is because it is his executive privilege to assert, on behalf of Holder and the DOJ. This is in anticipation of a contempt citation and, should the GOP wish to push it that far, an eventual court hearing.
It just sets the platform up for judicial review.
So you're saying this administration is clearly awash in transparency, right?