There is a big controversy over the current interceptor body armour which has been utilised in the armed forces over there in the states since the Bush administration came into power. Your average bullet proof vest is not stab proof, although it will protect against slashing knife attacks. A wire mesh is required to prevent a knife tip from penetrating and most vests do not contain such a mesh. There are numerous alternatives which only cost a small amount more and would provide significantly higher protection, for example, Dragon Skin armour provides level IV ballistic protection and is also stab resistant as I understand it. It's worth reading about, I'm surprised more people don't know about it. The majority of ranking officers in the US prefer to wear Dragon Skin but the average grunt doesn't have the privilege...
For more information refer to:http://www.bulletproofme.com/Quick_Answers.shtml#1http://en.wikipedia.org/wiki/Interceptor_body_armorhttp://en.wikipedia.org/wiki/Dragon_Skin_body_armorhttp://www.defensereview.com/modules.php?name=News&file=article&sid=842
As to knives as weapons, I still don't see how a stick could be any more effective. Again, I'm sure there are some CQB experts around the place who can provide you with better information. As I understand it, CQB is quite a different approach from standard infantry combat.
I believe that most of the CQB tactics in most military forces derives from trench warfare, where close combat was essential. Times have changed, although in urban combat, this kind of training may be more relevant.
Furthermore, the amount of time spent training knife tactics is apparently extremely limited anyway. Stuff like BJJ is supposedly far more consistently trained these days because it promotes physical and mental readiness in soldiers who may be asked to start a grappling match at any time as a conditioning drill. Various articles I've read promote this training method.