This advice to not fall asleep is pretty prevalent (at least on TV). Is there a basis for it?
One source on that: http://www.uamshealth.com/?id=10724
http://www.nlm.nih.gov/medlineplus/ency/article/000793.htm
PS: From you link "If the person who is injured is awake and holding a conversation, you can let him or her fall asleep as long as they are not developing any other symptoms such as dilated pupils or issues with walking. "