I'm not much of a conspiracy theorist, but I do like to have an open mind.  One of the 9/11 arguments that seems to get a great amount of play is the idea that the planes' jet fuel (!) couldn't have melted the steel in those buildings.  Popular Mechanics did a great piece debunking the 9/11 myths that explained it didn't need to melt the steel, just weaken it.

Anyway, I was reminded of the whole thing reading about this tanker crash in Oakland:

OAKLAND, California (AP) -- A heavily traveled section of freeway that funnels traffic off the San Francisco-Oakland Bay Bridge collapsed early Sunday after a gasoline tanker truck overturned and erupted into flames, authorities said.

Flames shot 200 feet in the air and the heat was intense enough to melt part of the freeway and cause the collapse, but the truck's driver walked away from the scene with second-degree burns.

No other injuries were reported.

"I've never seen anything like it," Officer Trent Cross of the California Highway Patrol said of the crumpled interchange.

"I'm looking at this thinking, 'Wow, no one died -- that's amazing. It's just very fortunate."

Authorities said the damage could take months to repair, and that it would cause the worst disruption for Bay Area commuters since the 1989 Loma Prieta earthquake damaged a section of the Bay Bridge itself.