What if the networks aren't deleting the content but just not distributing it to you? For example, Facebook determines what shows up on my newsfeed. If my friend posts something, and Facebook guesses that I won't be interested in it, it won't show on my newsfeed (I think) or it will be buried in the less important section. It may still exist on my friend's wall because he posted it, but I don't see it unless I actively go to his wall.

So even if the networks don't delete the content, they are already determining what we should and shouldnt see, no?