I just was going through old articles I had edited and found this vandalism dating back to 2008:
http://en.wikipedia.org/w/index.php?title=...oldid=229188334
"It is also the world's largest [[virgin]] convention attracting almost 85,000 participants from around the globe."
It was corrected a few weeks later:
http://en.wikipedia.org/w/index.php?title=...oldid=229188334
to this:
It is the world's largest convention attracting almost 85,000 participants from around the globe.
which stayed untouched for about a year until some guy added a "dubious" label:
http://en.wikipedia.org/w/index.php?title=...oldid=304425751
This article is far from the best article around -- far from it. Some guy just started translating all the Japanese language articles about Niigata into the English wikipedia. But, this seems to happen a lot. People from non English language places want information from their country or location in English wikipedia for whatever reason. But then, these can't be sourced properly. However, instead of keeping things out or looking for some way to properly source items, people say "oh, we don't know about such and such language or culture" so we should be careful.
I am assuming that was the thinking behind how this was kept in wikipedia for so long. Instead of someone doing a search or just using common sense, the few people that saw this article thought, well, I don't know, and didn't do anything.