A few weeks ago, I had a very interesting conversation with Fortune’s Sarah Silbert, one that’s still resonating with me. Silbert was exploring Uber’s marketing partnerships and how they might be different than what we see from Lyft and others. Her hunch was that Uber not only amplifies “the on-demand economy—it’s also setting the pace for a new generation of brand marketing.” The story was prompted by Uber’s many partnerships with brands, specifically the promotion to launch the new BMW 7 Series. But that’s…