I'm not sure what we are talking about here. Monopoly's on money, or monopoly's in general?

In a free market, I think monopoly's in general will almost certainly develop over things that are scarce. (Car's, food, computers, etc.) This is not a good thing, because it centralizes power.
Since you can use anything as money though (hence it is not necessarily scarce) I agree with you (Myrkul) on the money part.

Adrian-x: Yeah you could say that some meme's are a problem. However, there is absolutely no way to be sure that your meme is better than any other meme, since that thought itself would be (part of) the meme. Therefore, you should not able to force memes on anyone nor remove them. Neither do I really think you could be able to do so; a totalitarian society would be the closest thing to accomplishing such a thing. I'd say that shitty meme's are just something we need to deal with as best as we can.