Personally I feel that when music is put into categories/genre's they are given "Guidelines" not rules to make a track by.
Most Artists follow within the Guidelines but always end up making it their own/Different.
It's their own thoughts, emotions that are potrayed in their individual songs so classing it as this or that doesn't really accurrately describe what it is.
Problem lately is with all these new artists, they have to follow the "Guidelines" strictly and everything starts to sound the same, becoming very bland. They are not knowledgible enough to explore their music maker or just too afraid to go out there. ( Myself Included )
Already is rampant throughout Dubstep, but some bend the so to call "Rules/Guidelines" and make something unheard of.
The likes of Burial is a good example as is possibly Benga in a sense even though he's part of origins of the genre.
I've never heard of James Blake
But I'd make the time to listen.
( Sorry for the rant )