What determines the gamut of a sensor? In other words, what obstactles are there to creating one that captures a wider range of colors?

I ask because I have observed that the color in DV cameras uniformly sucks compared with 35mm and DSLRs. I think it is not just a matter of chroma subsampling, but the limitations of the NTSC color space.

How do HD sensors compare with SD sensors? Is there any information that one can use to compare the gamuts of the various HD cameras with SD and film?

As I understand it, gamut on SD and HD cameras are adjusted (downward) to match the standard display space. If the spec were changed, all the elements in the production and display system would have to be adjusted. The ideal time for this would have been 1995 when the ATSC standard was set.