These kinds of myths and frauds aren't unique to Wikipedia. For example, there's a myth out there that prior to the Vietnam War, soldiers were reluctant to kill the enemy, and that during WWII, about half of them would either refuse to fire their guns at the enemy, or would aim to miss. This story is repeated a lot, because it's an appealing idea. It paints human nature in a positive light, it says that fundamentally we don't really want to kill other people, and it takes a lot to get us to do it. In this narrative, people are fundamentally good, until the military corrupts us and turns us into killers. Unfortunately, it's a myth, based on academic fraud. The "discovery" is based on the work of a single researcher, who never published any of the primary data or interviews his conclusions are supposedly based on, and no one- certainly no military historian- has ever found even a shred of evidence to back it up. If you think about it for even a moment, it becomes obvious that it has to be a fraud. The Japanese fought to the death over those little scraps of coral in the Pacific, preferring to commit suicide to surrender. A group of Marines isn't going to be able to take those islands unless every single soldier is fighting with the willingness and intent to kill the enemy. Contemporary accounts of the battles make it clear they were bloody and vicious, and the behavior of American soldiers wasn't always merciful. One diary talks about machine gunners gleefully using parachuting Japanese aviators as target practice, and the skipper got pissed- mostly because they were wasting ammunition.
Years ago, this myth was exposed by an article in the New York Times. And yet the myth keeps getting repeated. A couple of years ago, I saw this nonsense being perpetuated- ironically, in an article in the Times. I wrote the editor of the article to complain that he was repeating something that the Times itself had debunked, and that they should publish a correction; they never did (the Times are a bunch of smug, lazy hacks).
I do think Wikipedia is probably worse for this than most other sources of information, but the bigger problem is that people are insufficiently skeptical. We assess information based on how well it fits what we already know, and what we want to believe- instead of trying to verify it. Slashdot is a perfect example of this- people constantly prefer to pull bullshit facts out of the air to support their opinions, rather than spend two minutes to read the original article or look up a statistic online.