Teaching tool...not finger pointing right? the new release of architecture revit 2008 has a nice little tool added called show history which allows you to see who has edited the model along the design and construction process. Refer to the image below, but it's
Show history -->
then select you're Revit model in question. This will help especially if someone had a computer crash and you're trying to find out who still owns elements that need to be relinquished or saved...