In a large corporate structure it's not at all easy to do. Funds get commingled together, they get used for different purposes, they come in from different directions. It might be easy for you and me to trace where our one source of income goes, but for corporations with multiple entry points for cash and exit points, in fact it is very difficult to track that in a very accurate fashion, assuming that is something you want to do in the first place.
On May 10th, 2007. See this statement in context.