[Bob]

Briefings usually consist of two parts. An oral presentation highlights the key elements. The document provides more detailed information and background. One important aspect of any briefing is that the person getting briefed has the opportunity to ask questions of the person doing the presentation.

By skipping any in-person, oral briefing, Obama ensures that nobody can ever testify that he was TOLD about any particular threat. It creates instant plausible deniability for Obama.

[RedEyeJack]

First, Obama doesn't have a clearance like underlings... he doesn't need one which is just as well because of his background he probably could not qualify for one (drug use, associations, etc). Second, with limited experience in dealing with such things I would guess that the code worded material in the written PDB would be HIGHLY controlled as in someone with the clearances and accesses would have to sign for anything that was handed over and would have to certify anyone, including the POTUS, who read it. Given some procedures of this sort, it is almost certain that (unlike birth certificates) there is an audit trail the DCI can track (in case there is a leak). They know who read the reports is the bottom line so the 40% figure is accurate.