Up to this point we've only talked about the relationship between individuals, because even large-scale one-to-many or many-to-many communication can be modeled as a series of one-to-one communications. As it comes time to choose as a society what restrictions we will allow senders to lay on receivers, it's appropriate to start analysing social effects.
Social effects of course arise from the combination of lots and lot of individual interactions. Some things only matter when lots of people do them; for instance see tragedy of the commons. Some effects only become obvious when you think about lots of people doing them. Since we have freedom on the individual level, we need to decide what effects as a society we want to encourage or discourage. After all, "intellectual property" law is supposed to be derived from the idea of managing social effects via legislating individuals:
To promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries; - Section 8 of the United States Constitution
We have to consider social effects because the ethics at an individual level can't guide us; there are too many possible legitimate answers.