The white one is #10 in Electronics at the moment. #1 is a HDMI cable.
The first 3 books on the Zune listed as most relevant have sales ranks of:
#58,213, #234,572, and #56,506. Comparable iPod books are ranked #25,759, #29,811, and #15,610.
While it's true that book sales aren't a direct measure of a product's popularity, there's certainly a relationship to the market size and interest.
It's understandable, from a marketing standpoint, why Amazon doesn't list overall sales ranks for products the way they do for books, but it invites manipulation.
Cheers,
Scott.