Again, these are all valid arguments. Alcohol is both hygroscopic, meaning it absorbs water, and to some degree, a solvent, so its use in a fuel system that's not designed to handle it can be problematic. Since the introduction of E-10, I've seen far more corrosion damage to carburetors and fuel tanks then I ever did previously, and an enormous increase in what I'd call "stale gas" problems, so yeah I think there's some real truth to that one. Anecdotally, I've also seen and heard of more than a few engines that suffered from mechanical damage traced to poor quality gasohol. Since no chemical analysis was performed on the fuel, I can't state positively that it was what caused the problem, but I know detonation when I see it, and the broken parts I've been shown were most positively caused by detonation that wasn't attributable to a lean mixture or overly advanced timing.