Speed Wobble

I cycled with a group of friends Saturday. It was a 30 mile ride, 50° weather, strong headwinds, rain, steep hills, and I was nearly killed by my own bike. In other words, it was great!
I learned something that day. The combination of cold (shivering), speed (45mph+ just coasting), bad bike geometry, and hitting the brakes, can cause some serious speed wobble.
Speed wobble, for those who have not experienced it, happens when your bike geometry, rider position, and rider weight combine to cause a sort of resonant frequency to be reached, which causes enough twisting in the top and down tube of the bike to generate wobble, especially in the front wheel. The natural tendency of the rider inexperienced with speed wobble is to hit the brakes, which I of course did. Apparently, this is counter productive, as I learned. An article by Jobst Brandt states:

When shimmy occurs on descents, with hands on the bars, it is highly disconcerting because the most common rider response, of gripping the bars firmly, only increases it.

and

Shimmy that concerns riders the most occurs with hands firmly on the bars and it is rider generated by muscular effect whose natural response is the same as the shimmy frequency, about that of Human shivering. Descending in cold weather can be difficult for this reason. The rider’s “death grip” only enhances the incidence of shimmy in this situation.

So, basically, all the ingredients were there for me to find myself donating skin to the Texas Department of Transportation. Luckily, I was able to slow down to where the wobble went away. The bad part is that now I want a new bike.
I did a little research on the hill that caused all this fun. Apparently it is a 15% grade for about a quarter mile. In other words, it drops 200 feet in about 1300 feet; very very steep. Riders regularly reach 50mph+, and often 60mph coasting down the thing. eek.
The hill: