I am encountering the shimmy problem on my LD bike (Columbus Spirit steel with carbon fork). With hands on the handlebar, the front end feels a little skiddish. With hands off, I definitely see the front end wobble. In reading the following article: http://www.sheldonbrown.com/brandt/shimmy.html, it seems to be 'inherent to the geometry and elasticity of the bicycle frame'. I got the bike built last summer for long distance events. I do not recall such front end looseness on a 300km brevet. The only major changes I have made after that event is tires. I had 700x23 Maxxi Refuse and changed to Conti 4-season 700x28. And a generic rear rack. Minor changes have been cosmetic: handlebar tape and bar plugs. I should add that I have noticed the shimmy on my commute runs - so the bike has a handlebar bag with things like wallet, cell phone, and glasses case. And the rear rack has one pannier (left side) with days clothes and food. I carry a similar load on my regular commuter (Kona Jack the Snake; alu frame with carbon fork) and I experience no wobbles.
Appreciate any assistance on how I can get a more stable front end for the LD ride.