The truth of the matter that in underground dance music is that most people dont bother with sample clearance because A: its too expensive and B: Not many people make enough money from there tracks to be worth sueing. Download sites (I would imagine) are the same as a real record store in that the liability is passed onto the creator of the track. If someone did raise an issue of copyright violation it would be you who had to deal with the consequences not the site/store. I think anyway lol.