I've read all of CB's posts and I can't see anything there that could possibly jeopardize operational security.
But of course, military "highers" would be concerned about issues of perception and wary about possible inadvertant disclosures of sensitive information.
I think it is reasonable for the CoC to review material posted on the web by service personel, and I can see no evidence of undue or excessive pressure brought to bear on CB by his "highers".
In fact, CB's own account of his interview with a senior officer about his web blog reveals both an appreciation for, and approval of, his online journal, right up the CoC.
Credit is due both CB and his "highers" that we, the public, can read his blog and gain a valuable insight into the daily lives of those on the frontline.
I've read all of CB's posts and I can't see anything there that could possibly jeopardize operational security.
My geuss is that they are concerned about blogs that indicate deteriorating morale. That information is of use to the enemy as feedback for the effectiveness of their operations. As in Vietnam, this enemy cannot defeat us on the field, they have to defeat us in our own minds. As a former intel officer, these blogs are what we used to call "indicators". Anything overly pessimistic or critical of the chain of command can be used in a variety of ways by the enemy (here and in Iraq).
And, since it come directly from the soldiers themselves, rather than through the filter of the press, it carries significantly more weight. What makes these blogs so interesting to us, is precisely what makes it potentially powerfull for use in counter-US propaganda.
There is a legitimate OPSEC argument here. Hate to say it, but it's so.