As typical for a discussion of memes (of the Richard Dawkins variety), I'm about to talk about something completely unoriginal to me, but that I've modified to some degree after thinking about it.
The thesis is this: there's a tendency for people to have more interest in explaining the spread of ideas they think are false, when compared to ideas they think are true.
For instance, there's a lot written about how and why religion spread through the world. On the other hand, there's comparatively little written about how and why general relativity spread through the world. But this is strange -- they are both just ideas that are spread via regular communication channels.
One could say that the difference is that general relativity permits experimental verification, and therefore it's no surprise that it spread through the world. The standard story here is that since the idea is simply true, the explanation for why it became widespread is boring -- people merely became convinced due to its actual veracity.
I reject this line of thought for two reasons. First, the vast majority of people don't experimentally verify general relativity, or examine its philosophical basis. Therefore, the mechanism by which the theory spreads is probably fairly similar to religion. Secondly, I don't see why the idea being true makes the memetic history of the idea any less interesting.
I'm not really sure about the best explanation for this effect -- that people treat true memes as less interesting than false ones -- but I'd like to take a guess. It's possible that the human brain seeks simple single stories to explain phenomena, even if the real explanation for those phenomena are due to a large number of factors. Furthermore, humans are bored by reality: if something has a seemingly clear explanation, even if the speaker doesn't actually know the true explanation, it's nonetheless not very fun to speculate about.
This theory would predict that we would be less interested in explaining why true memes spread, because we already have a readily available story for that: namely, that the idea is true and therefore compels its listeners to believe in it. On the other hand, a false meme no longer permits this standard story, which forces us to search for an alternative, perhaps exciting, explanation.
One possible takeaway is that we are just extremely wrong about why some ideas spread through the world. It's hard enough to know why a single person believes what they do. The idea that a single story could adequately explain why everyone believes something is even more ludicrous.