No I'm not. The Fizzbuzz article cited above is a wiki article. It is not based on original research, and draws from other articles. You will find the article I linked to linked to in a quote at the top of the first article in the 'articles' section of the wiki article; it is indeed the original source for the claim.
The wiki article uses as a source for the FizzBuzz statement the article at http://tickletux.wordpress.com/2007/01/24/using-fizzbuzz-to-find-developers-who-grok-coding/ . The wiki does not use as a source the article you just gave me a link to, which is http://www.joelonsoftware.com/items/2005/01/27.html and contains the "We get between 100 and 200 [resumes] per opening" quote. What you describe is neither the source for the statement, nor the first link in the articles section, but the second link in the article that is the first link in the ...
What is something you used to believe, preferably something concrete with direct or implied predictions, that you now know was dead wrong. Was your belief rational given what you knew and could know back then, or was it irrational, and why?
Edit: I feel like some of these are getting a bit glib and political. Please try to explain what false assumptions or biases were underlying your beliefs - be introspective - this is LW after all.