The motif of harmful sensation always intrigued me. My go-to "cached" example for this is the novel Snow Crash by Neal Stephenson, where properly-configured static can be used to "crash" a human's brain. I would guess that that type of thing, rather than the examples of people who have died laughing is what you're concerned about.
It doesn't seem obvious to me that a human-crashing meme would be able to spread though. Memes become viral because people spread them by showing them to other people around them and repost them to more and more places. If a human-crashing meme actually existed, (I think) it would be too virulent to spread effectively, much like how the most virulent of traditional diseases cannot spread effectively because they kill their hosts too quickly (the canonical example being Ebola, if memory serves).
Anyway, the death from laughter is an example of a meme that killed, albeit on an individual basis and without likelihood of becoming a true threat.
As I noted, crashing individuals is often possible. (c.f. the forbidden post, and the valley of bad rationality.) But something mass? As you note, it just doesn't work epidemiologically.
Of course, bad ideas spread quite effectively, as long as they don't kill their host.
Today's post, Superstimuli and the Collapse of Western Civilization, was originally published on 16 March 2007. A summary (taken from the LW wiki):
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