I don't know since I didn't remember reading any guidelines about awarding a DD . Its kinda murky to ponder on that and all I know is having a DD is having someone recommend this particular piece to someone and when they like it they feature it as DD which does not happened regularly to some awesomely epic pieces I saw that deserves a DD (not just the level of the art but the content itself and other stuffs that goes with it that makes you appreciate the piece above anything else that has the same category of art).
I don't really pay attention to DD's like... so I have no idea! I'm sure they deserve it if they get one though, It's just a spotlight, it's not really an award (According to DA anyways) so it's not really a matter of who deserves it or not, just what people feel like pointing out, I guess.
It's just a shame that there could be a thousand good artists that aren't well known, but don't get DD's because of it, I don't expect someone to look at all pics, just some people deserve recognition, especially for upcoming artists (hint hint XD lol joke, i don't deserve one ) to help them along.