Here is a good read straight from the olympic commitee on the 40 yd dash.. I found this trying to find some info to dispute those "i know someone that knows someone that ran a 4.10... "
here is a quick quote from near the bottom..
Veteran La Jolla-based agent Jack Bechta says Ron Wolf, the former general manager for the Green Bay Packers, explained it best to him once.
"He told me that there are guys who are fast but play slow, and that there are guys who are slow but play fast," Bechta says. "He told me that, sure, there are exceptions, but you can't have a team full of exceptions. Their thinking is, you can't take a good football player and make him fast, but you can take a great athlete and make him a good football player.
"You need a baseline, a common denominator, and that's what 40 times are. They are like minimum qualifying standards."
http://www.olympic-usa.org/11611_32384.htm