I know that guy in England. Many long time Stromtroopers here will remember him as well. I'll skip why he is not here on Stromtrooper and go straight to the problem.
The bearings are designed to withstand radial forces. Forces perpendicular to the axle. They are not designed to withstand strong thrust forces. Especially uneven thrust forces where one side is pushed and the other pulled.
The Gen 1 DL1000 cush rubbers, like all similar motorcycle wheel assemblies, is designed to cushion power pulses from the chain to the hub. These parts need to be held tightly between the rear sprocket drum and the wheel. However, the cush rubbers on the Gen 1 DL1000 are not held tightly between these two parts. This excessive play allows the chain's pull on the sprocket to apply uneven thrust forces on the bearing inside the sprocket drum. As the bearings wear due to these uneven thrust forces the chain starts to catch on the sides of the sprockets teeth. As the teeth catch on the chain the thrust forces on the bearings increase. As one gets worse the other does as well setting up a positive feedback loop that results in rapid bering, chain, and sprocket wear.
People learned early on that simply replacing the affected parts just lets them repeat the process and go through another chain, sprocket, bearing set, in another 7K to 11K miles.
I suggest starting a thread asking people if the spacer change fixed their problem or not. I suspect you will get many responses from people who had the problem and found it fixed afterwards, and many who installed the fix before having the problem who never experienced it because of their proactive action.
I'll check about starting a poll.