I don't have any data to back this up but my understanding is that to provide positive static and/or dynamic stability, most aircraft incorporate a design that has a tail downforce. I think generally that it wouldn't matter where the CG was located (either at the aft or forward limit) there would still be downforce on the tail. With an aft CG, however, there will be less downforce required to balance the aircraft and therefore you will have better cruise performance. Basically, the tail downforce acts like weight and has to be compensated for by lift (or a vertical component of thrust). To do that, you need to increase your angle of attack to create more lift which also creates more drag and slows you down. It's generally better to have a forward CG for recovery from unusual attitudes, ie: stalls or spins, and better to have an aft CG for cruise performance.
As you increase your angle of attack on the wings, your angle of attack on the tailplane decreases. You'll notice that as you decrease your speed towards the stall, you'll require more back elevator - it will be essentially an exponential increase in elevator deflection. This is partly to do with the decrease in speed (lift being a function of velocity squared) and partly to do with the decrease in angle of attack of the tailplane.
It is true that if you stall the tailplane, the nose will pitch down. With any stall, there is generally a buffeting action that occurs immediately prior to the stall. In a normal wing stall, you will feel the wings buffeting the whole aircraft. In a tailplane stall, the buffeting will mostly be felt through the control column. I would have to disagree that the tailplane is stalling first, causing the nose to drop. Of all the planes that I've stalled, I've never gotten the tailplane to even buffet. As a note, the tailplane stall recovery is completely opposite. To recover, you must pull back on the elevator assertively to break the stall.
So, what causes the nose down pitching moment at the point of stall? A lot of stuff.
1) The center of pressure will move backwards at the point of stall.
2) The amount of lift sharply changes - some people believe that lift drops off completely at the point of stall and that's why what happens at a stall happens. But, looking at a Cl vs AoA graph, you can see that that is not the case.
Take a look at this graph:
http://classicairshows.com/Education...Airfoil2CL.gif
You can see that at the Clmax, the lift drops off sharply - but it's still making TONS of lift! This airfoil stalls at what looks like 22 degrees AoA. Even at 8 degrees beyond the Clmax, it's creating lots of lift. But that's not analyzing the whole picture and that's why you initially don't think that lift still is high.
http://i.imgur.com/cKpPK.png
I've drawn a red line where, if you were able to continually increase your AoA and maintain the same lift, the Cl vs AoA line would follow. Essentially, about 1 degree beyond the critical AoA, the green line shows how much lift you've lost. So instead of being at 23 degrees AoA with a coefficient of lift of 1.8, you're stalled with a coefficient of lift of 1.15. At 1 degree beyond the critical AoA, you've lost 36% of the lift you should have at that AoA. The blue line shows roughly 6 degrees beyond the critical AoA. Not only are you losing a significant amount of lift, looking at the drag line you can see that at the critical AoA the drag rises sharply and continues rising at a high rate beyond the critical AoA. So, at the point of stall you're losing a significant amount of lift and, with the significant increase in drag, you're slowing down quickly - this is how you 'fall out of the sky'!
Going back to my points...
3) When you stall, your wings are essentially useless at this moment (not quite, but work with me here!) and you'd actually be better off without them. So, imagine that you're flying at a high angle of attack in level flight and your wings vanish. Just strictly based on the CG of the airplane, it will want to point the nose down to the ground. Not only that, but you've got that tailplane still there and if the CG was completely neutral, it would be the one to make sure that the nose pointed directly at the earth. It's now a missile heading directly for the earth. But before it can get to that point, the wings reappear and create lift effectively, ensuring that you don't nose dive the earth. Going back to the previous picture, you can see that a very small AoA increase at the Clmax point can have a drastic effect on the lift and drag. The same can be said for a very small AoA decrease at a point beyond the Clmax. So just as soon as your nose starts dropping down towards the earth like a missile, the wings come back to work and ensure that you don't dive straight down! You'll notice that the deeper the stall you enter, the more nose down the airplane will go and the above analogy should explain why.
Not all airplanes will handle exactly like that but for the majority of airplanes, that's pretty much the way she works - as I understand it.
Hopefully I answered your questions. If you have more let me know!
If you find some inaccuracies here also let me know.