It has been said many times before. In and of themselves, there is nothing wrong with re-grinds a lot of the larger profile regrinds will end up within .005" of the same size base circle of a "new blank" if a 24v 1998-2002 cam is used to regrind. As long as the reground centerlines are similar to what the factory centerlines were, then there is no problem, at all. The problem arises when people try to grind large lift grinds on centerlines differing from the factory units. When the whole lobe has to move over 5 degrees, a lot of meat has to be taken off of the cam to get the shape correct. This eats up metal on the nose as well as metal on the base circle. Eating up base-circle is of less concern but when you drastically change the shape of the nose of the cam where all of the pressure is, you get relatively soft metal in comparison to factory rockwell numbers. Soft lobes are no good for high rpm and spring pressure. It is a recipe for a failed lobe. 12v cores are the worst to regrind because the lobes are narrow and the centerlines have to be moved. Common rails are not much better. The lobe centers have to be moved a major amount, but at least they are wider to distribute the load of the tappet better. If it were me, I would only run a 1998-2002 regrind for a fairly aggressive cam. Mild grinds with low lift and narrow LSA's will be fine for CR and 12v cams.
The bigger question is why are people spending a lot of money on used/re-worked factory cams, when a new cam is not much more. I don't understand all of the cam guru's not having enough money to just ante up and have their own cams made. Why gamble with re-grinds? In most instances, re-grinds either don't take full advantage of optimum centerlines, or if they do they have very soft lobe noses.
One last thing. If a person couldn't afford to have their own cams made, do you think that they will tell you the whole truth about the dangers of re-grinds if that is all that they can afford to work with? Not a knock on anybody just a general observation on human nature.
Zach