Yeah, I'm basically of the same mind, mostly on the installation side.
I bought the bike second-hand, and the orig. owner had already had the fatter, wider bars installed. It seems that the wrench at the Harley dealer's shop that installed them didn't know to use a one piece clamp, chose not to use one, or they simply weren't available then. In any case, it's most certainly a combination of things that led to the bars failing: Drilled/slotted bars, excess torque due to the width of the bars, and using separate clamps for each riser.
One other thing for those of you planning on mounting a one-piece clamp:
Be prepared to need to squeeze the risers a touch (1/16"-1/8") in order to get all the bolt holes to line up properly. I used a bar clamp to do it, and it worked out just fine.