I agree with all the posters who have shown up the potential faults for both rings and radials, they are all possible as are the resulting issues.
However, I don't think anyone should design an installation (or part of one) based on how someone could mess it up by fiddling around with it either in ignorance or when incompetent. The only considerations in that vein should be given to potential users and uses, not some idiot with a screwdriver. It's part of the human condition that some people will mess about where they shouldn't, some will be lucky, some won't. As long as all the professionals involved have done their job properly then all is well IMHO.
Design and planning is about selecting the correct methods and materials for the intended purpose. Radials, rings, and combinations of the two are all available to use. It's up to the designer and installer to select what he or she thinks is best suited to the situation in front of them, then use that.