Phase One has announced a mono version of its 100MP IQ3 medium format camera back. The $50,000 camera has no color filter array or IR filter, so should produce higher levels of pixel sharpness as well as offering greater sensitivity. It can integrate with its IQ3 XF camera as well as being compatible with a range of other medium format cameras.
When it comes to the 'why?' question, Phase One talks about 'timeless expression' and suggests it will appeal to photographers engaged in 'fine... more (link is external)