The problem I see is reddit isn't an aggregator in the strict sense. Look at the front page, it's riddled with imgur links. How many of them (advice animals, original content, etc) were posted there just for reddit? I'll just say unscientifically, a lot. (After all, that's why imgur was born.)

So you're a site with a major feature that (a) drives publishers to another site, and (b) drives viewers to the same site, even though (c) the content was created for your site. And now (d) that site is adding some of your core features. I guess I can't see how that isn't a blindingly obvious concern if you're running reddit.