Oh, also.

Imagine I find a meme. It's awesome, but has a stamp on it.

Why should I assume that the stamp is from the person who made it?

One could argue that, if I am going to share the meme, it is my responsibility not to potentially mislead future viewers of its origin. Perhaps the only good option is to remove it.

Further, if it is a great meme, and I go to find the person's account or website who put the stamp on it, and find that they have a bunch of memes I disagree with, lets say they promote kidnapping children, for instance. Perhaps I am obligated to remove it, and to find as many meme contests to spread it in as I can.

This is partly ridiculo absurdum for demonstration purposes but I think illustrates that there is perhaps a defendable position that the only practical policy is to let everyone do whatever they want with memes. (and let anyone who wants to downzap them, of course).