The next time he came out to shoe, I asked him why he did this and he 
explained that it was to make the horse break over faster behind...in 
essence by tricking him into thinking that his feet were somewhere other 
than where they really were (i.e. tripping him on every stride).
I told him not to do that anymore, that I would find some other way of 
keeping my horse from forging.
At the same time, I discovered that he (this is not true with every 
horse) only forged (cosistently) when he was under saddle.  Not at 
liberty.  Which led me to believe that this was clearly rider error. 
I found that he showed a marked tendency to do this when he was not on 
the bit, but had his nose stuck up in the air (he was a green arab) and 
had hollowed his back.  This was accentuated when I rode him because my 
weight was causing him to hollow his back even more.
As my horse developed the muscles and the training to round his back and 
support my weight....the clicking disappeared.
Additionally, that "clicking" is a very useful training tool...it tells me 
when my horse is not in a nicely rounded frame.  In the early stages of 
endurance training, a horse will not have sufficent strength to support 
the rider's weight for the entire ride...this is an indication that the 
horse's back is not sufficiently prepared for the extended effort.
My recommendations to people who have horses that forge is...train your 
horse to round its back, develop the physical strength to do this, and 
use bell boots to protect the fronnt feet until the horse does.  At the 
same time, trim the horse to its natural hoof angle and shoe it so the 
shoe is a natural extension of the foot.
My farrier does not do any "corrective" shoing.  I do "corrective" schooling.
Just my 2 cents.
kat
Orange County, Calif.