Dr Hawkings assertion that the information we need to understand black holes is recorded on the event horizon? Exactly what is he asserting?

Don't give Hawking credit for that. It was not his idea.

This is the basis for the so called holographic theory of the black hole. Quantum mechanics requires that information is never lost to the universe. It can be scattered around, but never lost (information in quantum mechanics is the quantum state vector which is all that can known about a quantum system). When Hawking proposed Hawking radiation, he claimed that the radiation that was emitted was random and contained no information about what went into the black hole. Since this violated a pillar of quantum mechanics, many were uncomfortable with idea. Since then, theories have shown that information can be retained at the event horizon, and Hawking radiation is encoded with that information so it is not lost.

This however created a seeming paradox. There is a theorem in quantum mechanics called the no clone theorem which says the laws of physics will not allow a state vector to be cloned without destroying the original state vector. You can't produce another copy of the state vector and still retain the original. This presented a paradox since information does pass into a black hole yet it must be stored on the event horizon in a way that can be emitted. A proposal was made that the black hole had some of the properties of a hologram which could resolve the paradox.

The resemblance between a black hole and holograms in everyday life is really just conceptual at best. Holograms store not only color and intensity of light like a phtograph, it also stores interference information on its 2-d surface. The interference information allows it to store 3-d relationships on the 2-d surface, as well as color and intensity. The analogy with a black hole is that 3-d information is stored at the 2-d surface of the black hole, and the 3-d interior of the black hole is in some sense a projection of the surface information (it's of course much more complicated than that).

While that may seem a little ( or a lot) crazy, various theories and calculations show that the entropy of the black hole is strangely dependent on the area of the event horizon and NOT the volume of the black hole as would be expected. Since entropy can be a measure of the total number of states within the black hole, which in turn is a measure of the total amount of information possible in the black hole, having that depend on the area of the event horizon seems to indicate that 3-d information is store in a 2-d event horizon region. Interestingly, the entropy of the black hole is proportion to the number of Planck 'bits' that can cover the event horizon.

1) He is asserting that black holes with their "event horizon" really do exist.

2) He is asserting that information just prior to an object disappearing over the horizon is "stored" somehow (as if by magic) on the black hole, conveniently there for us to study.

As always, we can never learn what is actually beyond the horizon, because to do so would mean that there really is no event horizon, and thus no black holes.

Cheers!

Here is a short answer that skips a few steps (there are gaps), otherwise the full answer would go on forever.

From Relativity, as objects fall towards a black hole, we should perceive their time flow as slowing down. Since the escape speed at the event horizon is equal to the speed of light, this means that (from OUR frame of reference), we would see the object as stopped at the event horizon -- or more precisely, we would see the object approach the event horizon going slower and slower, never quite reaching it.

From the frame of reference of the black hole (at least, at the event horizon), space itself is falling into the black hole, forcing that region of space to expand differently (and much faster) than space in the rest of the universe.

From the frame of reference of the infalling object, even though it is moving through its local space faster and faster, the distance separating it from the "inside" of the black hole is not getting smaller... because local space is expanding too fast. Therefore, it will never reach the "inside".

One way to satisfy all three viewpoints (mathematically) is to assume that any object falling "into" a black hole, never makes it past the event horizon. Therefore, all the "information" (mass, charge, etc.) remains on the event horizon and it is not "lost" inside.

This interpretation (by Hawking) comes from him having lost a bet, where he had said that (mathematically) all information is lost about any object falling into a black hole ("black holes have no hair"), but somebody else proved (mathematically) that he was wrong.

It does appear that the information is not lost, despite the idea that a black hole is a region from which the escape speed is higher than the speed of light.

The only way to reconcile the two viewpoints, as perceived from our frame of reference (safely outside the black hole) is to accept that matter never actually makes it "inside", but gets collected on the event horizon.

He is asserting that theoretical physicists need to have plenty of money thrown at them so they can spend more time doing stuff that is of absolutely no use to society.

There is no such thing as a black hole, at least not as General Relativity describes it — an object so massive that light cannot escape from it. In reality, light is unaffected by gravity. Light only bends in refractive index gradients like in atmospheres or galactic cluster gas. Unfortunately, in order to prop up the fallacious Theory of Relativity, mainstream science generally labels such refractional lensing as gravitational lensing.

If gravity bent light, stellar "Einstein Rings" would be visible all over the night sky, wherever one star lies behind another — there are none. The stars orbiting Sagittarius A* at the centre of the Milky Way (supposedly the location of a black hole) would also display obvious signs of gravitational lensing — they don't.

This lecture can tell you more: http://www.youtube.com/watch?v=CnvOybT2WwU

Not the "Holographic Universe"
It is a requirement of quantum engineering (to make the maths work) that information is never lost. The maths works but it is an entirely unverified assertion. Hawking et al have reified this concept to the point of saying that information has reality in itself. Now a particle that is engulfed by the event horizon has no informatin other than the type and colour of the particle (not actually colour - it's a code word).
So Hawking radiation decreases the Black Hole by emiting particles with no information - so where did the information go?

Hawking holds that the information is never engulfed - it moves out as the event horizon expands and "magically" attaches itself to newly minted particles emitted as Hawking Radiation. The fun part is that he says the information has a location but instantly flashes to the emitted particle (this is faster than light information transfer which is also forbidden).

Hawking asserts this with zero evidence, others agree with the Great Man. So they are saying that information has a reality of its own and that it ignores relativity. The late stage of all great physicists tends to extreme assertions along with "be afraid of the aliens".

Jh