I suggest just not putting them in the wrong way...Are you really going to be in that much of a hurry that you won't stop to think which way they go in?
Wrong way = chance of bad things. Taking 2 seconds to remember which way the batteries go in = good.
[quote author=litedisorder link=1239238525/0#0 date=1239238525]What happens if you put the battery in backwards? Will it hurt the laser? It seems like it would be easy to do because of neg. end going up in host.