But we can't assume the comments in this forum, even if the majority prefer the case, represent the entire customer base. Besides, feedback like this is rarely black and white; typically developers will ask customers something along the lines of "if we implement a shiny new faceplate, could you live without the cover?". And the problem with if/then scenarios like that is that respondents are pigeon-holed into "lesser evil" sort of answers or they fail to consider all of the repercussions. Generally this is just piss-poor poll design (which is far too common IMO)... but not having seen what Nokia used I can't say that this was for sure the case.

EDIT: oh, and by the way, I've come up with a perfect way to include a cover for the N800's faceplate. After I model it I'll post the design.