As I recall (yeah I was a COG guy once) that's not plating. It's pitting of the hardened / ground casting. But because the cam exerts force across a wide surface area, those swiss cheese like holes are of no significance.
I was also a COG member and remember many discussion of this exact sort of problem. I never had pitting on my ZG1000 cams, but as it happened, I had an unusual problem with my C10, the oil line feeding the cylinder head got blocked with a piece of oil filter media (happened before I bought it, yes I am mr. lucky) so no oil got to the head. No surprise, the cams and all the rockers were well and truly ruined by that- and that damage looked
nothing like this sort of pitting. Plentiful scoring, and lots of metal worn off the lobes and the rockers. I unblocked the oil line and replaced the cams and rockers with a used set from a fellow COGer.
Fast foward to this year, and when I was doing a valve adjustment on my wife's new-ish (2009 model, bought new in June 2010) EX500, lo and behold I see what looks almost exactly like the pics I used to see on the COG forum. Only about 8000 miles on it, and one exhaust cam lobe has the characteristic pitting. I used good quality oil and filters, changing the filter at every oil change:
Chevron Delo 400 @ 563 miles (first valve check)
Shell Rotella 15W-40 @ 3200 miles
Shell Rotella 15W-40 @ 7086 miles
Mobil Delvac 1300 Super @ 8170 miles
I don't believe for a minute this is an oil-related failure. The EX500 valve train is exactly the same design as the ZG1000, just half as many cylinders, and uses the same rockers, and I suspect the cams are made of the same materials and share the same manufacturing process.
I am going to keep an eye on it, but unless it develops an unbroken line of craters continuously across the width of the cam, I really doubt the dropouts will cause a problem.
Also I am not too worried about it. Mostly because, I already have a spare EX500 engine with low miles, with no pitting on the exhaust cam.
