Frankly, unless there is a weight or heavy knot at the end of it, or unless it is wrapped around a firm metal rod of some sort, it isn't for self defense. Possibly for survival, but the only Paracord self defense items right now have one or the other, as you really need a weight/knot at the end or that firm metal rod for it to do any good. Unless you are a ninja, that is. The only other possible self-defense use I can imagine is if you use the free end of the cord itself to swing your keys, at which point you'd best have a good deal of weight in keys or you'll do little but annoy someone, if that.
Hope that helps!