[Xanthion]

Oh, no doubt. It can be fantastically efficient. If you've got the strength, it's a good idea to slam their nose into your shoulder when you do it.

However, I prefer attacks to the groin to be either stomps (Ouch) or rips (Really ouch). The main reason is because it has the potential to turn the predator-prey dynamic around. When you're attacked, the attacker is the predator. He expects pain, it's part of being the predator. The key to turning it around is moving beyond pain. You need to go for permanent damage. Which is what makes the eyes fantastic.

Men take hits to the testicles far more than nature must have intended. All physical sports carry with them the potential for pain to the genitals. It's a risk you get used to. And yes, it hurts. But it usually causes no long lasting damage. However, someone trying to jab something into my eyes is a new experience for me. It's something that's hard to recover from, and puts you very much on the defensive.

Tear, bite off, gouge out whatever you can. If they can't grow it back, or heal with time, the prospect of losing it is terrifying.

EDIT: as to the martial arts - I'm not familiar with Krav maga, but it sounds similar to the martial art I study, which is Kupso. Kupso's more or less localised to Scotland (But not a traditional Scottish martial art :P). It's used by bouncers/security guards a lot (In fact, both the instructors work as bouncers at my Student's Union). Has a lot of focus on real life situations, as opposed to the predominantly "form over function" tournament martial arts.