I really like this video on memes, if only because it brings up a point I haven’t seen since The Selfish Gene.* Memes don’t exist in isolation but within an ecosystem of other memes. If two or more of them cooperate together, they can survive better than memes which do not.
I do have a minor gripe, though. The video implies that the truth of any given meme is arbitrary, and that segregation is a natural outcome of conflicting/cooperating memes. Both aren’t true; in any argument with two or more well-defined sides, all but one is guaranteed to be false or incomplete, and even that one isn’t guaranteed to be complete or true. This is why the Argument to Moderation, or taking the middle-ground approach, is usually wrong. Memes may not care about truth, but human beings do.
As a consequence, this segregation is actually due to human factors and not inherent to memes. False statements tend to be disavowed or forgotten by humans over time, due to confrontations with the truth. So if a false meme is to survive in humanity, it has to wall itself off from memes that could challenge its truthhood. Typically this is helped along via other memes; your opponents are emotional or irrational, on a witch-hunt, just looking for something to be angry over, and so on. In extreme cases it really is a physical segregation, or at least an active avoidance of the “opposing” side.
As powerful as meme theory can be, it’s useless without also considering the carriers of those memes, or a bit of philosophy.
* I might be misremembering, but I think Dawkins suggests that bundles of memes can cooperate with one another, in the context of religion. It’s been a few years, though.