[Klaus]

I suppose the only reason for this can be a patent violation.
If this is true they certainly got mail from Canon.
However, if so it also means that Sigma/Tamron will have to wait for 10(?) years after the patent was filed.

I sort of doubt that this strategy is helpful though. It may help with profits in the short term but unless you are a fanboy, it would make the system a no-go.