thats a bad assumption. people sell alot of things until there is a problem. i think you can still buy cast aluminum wheel spacers. these can crack and fall apart, the billet are better but i'm sure no one has done the proper calculations and or testing. afterall we are talking about this because people want to take the easy way out and not spend the money on forged wheels with proper backspacing. that being said, there are tons of companies making aftermarket wheels so for 98% of the people who just want to look cool they will most likely be fine. however if you're racing i'd spend the money on the proper equipment