[dvt]

Wikipedia's sources are usually terrible (a blog post), unverifiable (I don't have access to the actual book), or they 404.

Sometimes, Wikipedia editors don't understand the source so the Wikipedia article and the source are actually at odds with one another. I've witnessed this a few times when I investigated dubious claims.

[VintageCool]

One time while studying for a final exam, I did a final review of the Wikipedia article and noticed a quote which was an exact match for a paper that I had just read, and it was followed by [citation needed].

Adding that citation is one of my proudest Wikipedia edits ever.