Oh my, I get to stand on my soapbox again!
First off, I make a variety of Alliance designed latex weaponry. You can see them at
http://www.larping.net and follow the link to my latex work. To my knowledge, for the last 5 years any of my weapons made under the Alliance weapon construction guidelines has never failed inspection at an Alliance game. Note, however, that ANY weapon can be failed by a weapon's marshal and just because the ones I make I am able to use at my games does not mean that they would pass in another chapter - even if I follow all the rules to the letter.
Now, the only reason I can find that a latex coating isn't allowed is that in very cold weather, the latex will become harder than duct tape or cloth. This adds a certain rigidity to the weapon and makes a very hard striking surface. If you add that to the sword designs of latex weapons (having a thin edge), that can cause some major injuries. I asked the makers in the UK what they do to combat this issue and they say "we just fight a bit more careful in winter." But as their games involve a very low hit point system (often one-three valid hits dropping someone) whereas the Alliance rules is about hitting your opponent as quickly as possible, such safety isn't practical with the general playerbase.
I have done the best I could in researching LARPing injuries due to weapons. I spent 6 months contact both major and minor groups to see what they had to report. The worst injury I heard about was from an Alliance player where one of the swords at a winter event where they were allowed (not Alliance) wound up tearing his ear and opened up a cut between the ear and the skull. Meanwhile someone broke his rib and I think punctured his lung with it when he fell on an Alliance style dagger. Other than that, I have received no reports about any injury caused by latex weapons that caused someone to have to leave an event to seek medical attention.
I have played in Alliance and NERO games that have allowed and that haven't allowed latex weapons and I have received more debilitating (painful) injuries via the boffer weapons than the latex ones. I have even received the infamous 'sword point to the eye' a couple of times with a latex weapon and all it resulted in was me sitting out of the combat until my eye stopped tearing. The same has been true for those times I've been hit in the head or eye with a boffer weapon.
In my opinion, latex weapons are no more dangerous than boffer ones. In fact, I find them safer due to them having less mass and thereby greater control and generally lighter impacts. But really, it all comes down to the person wielding them. With Alliance though, the boffers are probably the better choice.
