I think that you have not received any DD's you didn't deserve.

How do you know if you've got a daily deviation? Do they notify you?

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.

just a quick question how do i check the daily deviation?

A lot of the pieces are nice in the DDs but some I scratch my head in question well that and the over abundance of anime DDs which tend to all look the same to me.

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.

most do, but sometimes it seams that they are featured just cause they couldn't find anyone better.