Excellent post Morgan...thankyou
Here is some more info on the matter from my personal experiences. I too had the same problem on the MY02 STi (that car had Australia's very first DBA 5000's made for a Brembo equipped Subaru...they were prototypes given to me by DBA for testing and they let me keep them!)....they were on the car for almost 4 years and it was only in the last year or less that the clicking started...at first just noticable, but it got worse.
I used to get it only while turning and with the brake pedal depressed (ie pads against rotor) it went away.
I tried chamferring the pads (DS 2500's) and it went away for a while then gradually came back. MMS were very skeptical about wheel bearings being the issue but I replaced them anyway since one was a little dodgy...no clicking for a week then back again! I put the standard rotors on when I traded the car and of course the problem disappeared, though I still experienced some pad knock off. So in the end I put it down to pad knock off making the edge of the pads catch the slots in the rotors. I put the pad knock off down to slightly cooked piston seals on the Brembos due to 4 years of motorsport.
I also put the problem to DBA back at the beginning of 2005 and they couldn't offer any explanations, so I'm happy you kept at them to work it out, though I still suspect there may also be some other additional minor factors at work. I have the DBA 5000 rotors from the '02 (albeit another near new pair) on the MY06 STi (but with new 114 PCD hats) and so far no problems at all...it will be interesting to see how they go over time. And the brakes have been fairly hot on the '06 too (at Collie)...in fact hot enough to turn the red "Brembo" writing on the front calipers black!