...used to have a black carpet in my bedroom when I was a miserable teenager...it was awful, always covered in bits and crumbs and fluff etc...my Mum got fed up of hoovering it for a start so I took over doing it which was a good excuse because I didn't really want her in my room, she might have found my stash of Club International.
Home cinema down in the basement is carpeted in black. Doesn't take any longer to vacuum than other shades. Only downside is that the spiders can sneak up on you more easily.