I know that asking Dave Winer to check his facts is a bit like asking a dog not to bark, but . . .
I just finished the history of the Johnstown flood, by David McCullough. I was only peripherally aware of the event, but it was the biggest news in the US since the assassination of Abraham Lincoln. More people died in the flood than on 9-11, and it was caused by human arrogance, the very richest Americans, including Andrew Carnegie.
According to the Johnstown Flood Museum, 2,209 people lost their lives in that tragedy.
On September 11, 2001, at least 2,985 people were killed as a result of a series of coordinated terrorist attacks against the United States.
The last time I checked, 2,985 > 2,209.