So long as there isn't a hidden monopoly ... that would act against our interests.

I don't care who makes anything so long as there is a clear and accurate statement of the manufacturing plant.

I do find it strange that the "own brand" lens lineups of the "big two" DSLR brands have so many lenses which have the same focal length and aperture ...

There is history here. Some of the later Olympus OM lenses were made by Cosina to Cosina designs. I don't object to this on principle, just that the name Cosina does not appear anywhere on the product, its documentation or its packaging. Whatever the merits of these lenses (some of them were perfectly OK) I feel that describing them as "Olympus Zuiko" was (at the very least) misrepresentation. They should have been prominently labelled "Designed and manufactured by Cosina for Olympus".