Charlie is correct that anodizing reduces the fatigue life of aluminum parts by "up to" 50%. The Anodizing process makes the surface of the aluminum brittle. This is why the fatigue life is reduced. Fatigue life reduction is related to the thickness of the coating and the chemicals used. See
The tests cited were for 7000 series aluminums. Not sure we use any 7000 in our planes. Also, failure was listed at 5 million cycles.
I think you guys are concerned about a problem that doesn't exist. As evidence, why are our spars anodized? Should we refuse them? Why aren't spars failing? Why are our AN plumbing fittings anodized blue? Should we be concerned?
I am very confident that the engineers at Boeing would not be anodizing Apache parts if this was a concern. Further, I'm confident that the engineers at Van's would not have anodized the most critical part in our planes, the spar system, if there was concern.
Again, if you want anodize some parts I believe it is safe and you're not likely to experience a problem. The internet is both a blessing and a curse sometimes.