this is something i see everytime i choose the "videogame" genre, as everyone can see there are a lot of songs from doujin circles and sometimes some remix from youtube or nicovideo. I think that makes harder to search some songs (example: search touhou project and u will get 21 pages of songs and more than half are from doujin circles) so, i believe it's a good idea if we separate this songs (if someone wanna seach all the songs including the doujin circles he/she can use the tags). If the video is some type of video from youtube or nicovideo it should be classified as unspecified or some new type of genre, in this way people who search something new but at same time a little specific.