Having a track sampled in a remix or mashup might seem good for the original artist, but that doesn't mean their record label won't try to shake SoundCloud down for cash. Especially if soundcloud start making money (and why else would VCs have invested?).
This is certainly true; at some stage soundcloud though has the potential to be the label, though. Or in other words, to be the distrtibution channel as there is no/limited physical need to press records, when DJs are downloading the tracks. With this in mind, your point still stands, but the role of the label being more of a marketer is its highest value added service. And in that role, it would seem they would want to encourage promotion of the tracks. The open issue is the monetization of that scale by the two parties, who gets what cut. And that is going to continue to be fought over...regardless of who owns/controls the copyright...as that will also be in flux going fwd imho. But we shall see....
