Stock Car Science has written a very nice blog about just how those Goodyears work (or sometimes don't work). Hopefully part two of her blog on this subject will deal with the Crew Chiefs pushing the camber limits over specs and other factors which can cause even the best tires to wear prematurely and fail.
It seems to be a fine line between what drivers want and what Goodyear (and Nascar) determines to be a safe tire for a race venue. But I'll say this, Nascar should stick to a single tire supplier, as a 'tire war' (as seen in the late '90s) would literally kill the sport. (as well as put driver safety in great jeopardy) The problem is that CCs and team owners would use the softest tire available and most aggressive camber setting, simply because it would make them faster. All the while, the tire manufacturers would be in the business to SELL tires, and would be forced to make an even softer tire. The domino effect might never end until the unspeakable happens.
But go check out Stock Car Science, its worth the trip.