Russ-
Thanks for the posting, but now you've got me wondering, especially since you infer that a registrar wouldn't consider my example preventive action.
Your point about applying it to processes makes sense, but I'm not convinced that applying PA to individual parts is inappropriate. Are you saying that, for example, establishing a guideline to ensure that future molds have proper radii (affecting the process of design) would qualify as PA, where simply fixing something that already exists, even though you're preventing the potential problem from showing up, would not? I can kind of see that. In fact, as I write this, I'm agreeing with your original statements more.
One other comment, with all the debate over CA vs PA, the registrars I've dealt with seem to be happy as long as you're doing something/anything.
Alf