Blue Mountain
Resident Skeptical Hobbit
#4 (Take this, metallurgy!). The other front runners (Proof by Microsoft simulation and Twin Towers: There can only be one) actually show a certain amount of applied intelligence. While the thought that people who are aware enough of the world to use a flight simulator and know that the Petronas Twin Towers exist (and have a concrete core) are simultaneously clued out enough to post what they did on an internet site is scary, the sheer cogitational failure of the poster who said "steel does not melt, ever" is truly mind-boggling.