The sensor is as fundamental to digital photography as film is to film photography. As there have been a few major film camera companies who were also film manufacturers (Fuji, Kodak, Konica...) so there are digital camera companies who are sensor manufacturers - funnily enough, many of the same ones (Fuji, Kodak, Konica -> Konica-Minolta -> Sony and now Samsung.

Samsung's collaboration with Pentax (and their association with Hoya) give them the expertise in optics, which complements their experience in electronics and semiconductor fabrication to cover all the main systems of modern digital cameras.

All in all, I think it's a good thing for photographers to have another manufacturer that can innovate in all parts of the camera design.