I don't see why people on here think "Dark" music is so mature. "Dark" music from pop musicians sounds more like a teenage rebellious phase rather than anything particularly mature to me, there's a reason Katy is the most successful pop act on adult radio formats whilst most of her peers are ignored.
Though if Dark Horse, E.T., Dressin Up and Wide Awake are examples of dark music I guess I don't have any idea what dark is.

(50% of them are horrible anyway)