Yes, I thought about mentioning something like that as more borderline.
On one hand, it might be legal, deciding the agency is in the person submitting the link and the other person is only automatically shoving some bits around.
On the other hand, you might decide that that's not a service that can legitimately be paid for. Some things can't be outsourced. I think right now that it's legal to 3d print a rifle but it's not legal to have someone else print it for you (but I'm having trouble finding references).
Either way, the intent of the law matters, and it's possible to outlaw commercial enterprises based around piracy but not individuals' actions. One method might be to limit the number of 'uploads' to a number like 10.