Kenny,
I don't see how that is a design flaw, your example was the owner not properly maintaining his vehicle. On a side note about that, for those using adaptors, use Locktite on the lug nuts, then torque them down. I would still check them, but using Locktite gives a little peace of mind.
I have adaptors on my Z to run Honda wheels and never had a problem with them. Hell, I have 2 inch thick adaptors on my '02 Chevy S-10 Crew Cab to push the track out to fill the factory flares and to match the track width of the front wheels. I have had them on for at least 20,000 miles now and have had ZERO problems with them in a 4,000 pound truck that every now and then pulls a 1,800 trailer with a vehicle on it. I also take it off roading every once in a while too.
As long as you buy the adaptors from a reputable company, you should not have any problems.