Bike Anti-Porn - When Things Go Wrong

If it's a carbon steerer on the fork then one spacer above the stem is sometimes the prescribed way to set it up.
Bontrager for example send a note in the parts box that you have to put one spacer above the stem to move the stress point down a bit as clamping the stem on right up at the top can cause the steerer to collapse.

Naughty Alberto!
http://cdn.mos.bikeradar.com/images/news/2008/05/29/08---headset-850-65.jpg

http://www.bikeradar.com/gear/article/pro-bike-alberto-contadors-astana-trek-madone-16689