OK, my turn.
I don't buy LIHOP, any variant of LIHOP, and I'll tell you why.
LIHOP is inherently more difficult to prove either way. We're speculating about what people knew, not what they did, and so it's harder to find evidence one way or another. We accept this.
In Lawrence Wright's excellent The Looming Tower and numerous other places, we read about dedicated CIA and FBI agents named Michael Scheuer, John O'Neill, and Dan Coleman among others. These folks were focused on bin Laden, long before the rest of us were. They ultimately couldn't figure out what was going on in time, not having access to all of the evidence they would have needed. But they were perhaps closer than anyone, at least closer than anyone that I've read about.
We also accept that the intelligence services of the United States don't work terribly well. This is no reflection on the individuals therein. Any bureaucracy runs at a fraction of its theoretical potential. The Government, in general, is a clumsy, stinky beast. Everyone knows this. Plato knew this.
Suppose LIHOP is true. That would mean that someone in power knew much more than these agents did. Who is this mystery person? How was this knowledge gained? Whomever this person is must have somehow stumbled upon the motherlode of information, despite being nowhere near as focused as they were, and escaping all mention afterwards. But more importantly, they must somehow have failed to hear about this.
But there's more. LIHOP requires that they were prevented from hearing about this. They weren't taken seriously enough by their superiors, if I read the stories correctly -- so why would they have been singled out? How could this blackout have been inflicted upon them without their knowledge? It couldn't have been an accident.
If we try to do it the slick way, i.e. put in seemingly innocuous procedural roadblocks and cultural hurdles to stymie them, then the person doing this must have known a lot more than they did. These things take time to implement. Whomever allegedly carried out this kind of interference -- essential to the LIHOP hypothesis -- must have known about the plot from the very beginning.
I simply don't buy it. What emerges in the story of John O'Neill and his fellow agents is the story of a man searching frantically for a needle in a haystack, but who could only get to half of the haystack. This is entirely Business As Usual in any government agency. LIHOP requires that they were blocked, subtly and skillfully, and that requires an absolutely incredible prescience and influence on the part of whomever blocked them. Not only blocked them, but only just blocked them -- allowing them to get dangerously close to unraveling the plot -- and did so with such gentle finesse that they never even sensed it.
Ridiculous.
MIHOP, by the way, fails the same test, and fails it more spectacularly. For MIHOP to be true, they all must have been totally barking up the wrong tree the whole time. Or liars. Or in on it.
This is just another example of how conspiracy theories tend to "inflate" upon examination. All the assumptions the conspiracy folks make have consequences. Eventually, the weight of these consequences brings the whole theory to a catastrophe of illogic and self-contradiction.
I don't doubt for a moment that the Government needs fixing, or that there's a healthy amount of buck-passing and butt-covering in the investigation that followed. But this is NOT the same thing as accusing the Government or anyone in it of being complicit, either actively or passively, in the murder of thousands. Those accusations are totally out of line, and those making them on such scant basis should be deeply ashamed.