As the Thread title says things like Nico Nico Douga (also Bili Bili Douga), YouTube or BandCamp (http://osu.ppy.sh/forum/p/1811932) should never be used in the Source or as Artist. It's self-explainated why and it should be set as official Rule. It has similar reasons as the Vocaloid Rule.
Websites should not be used as Artist or as Source. Make sure that the Maker of the Song creates its works on this website.