In reply to Heike:
I agree with you, even though I am not a pacifist. I think war is a serious business and not a game, and should therefore not be emulated in games. That said, all my children wanted and got toy pop guns and squirt guns, even my girls, and my son for a while spent most of his pocket money on Nerf guns (which are now lying unused in some box in the attic).
In general, incorporating war and fighting into play is just as natural for children as is playing family. Any three year old will pick up a stick and turn it into a sword or gun.
I therefore cannot really pin down why sticks and Nerf guns are OK for me, but laser quest, first person shooter video gamess, or paintballing are not. Maybe the latter are too close to the real thing, so the desensitization towards violence outweighs the beneficial effect of practising in play dealing with conflicts.
I have not let my children join such parties the few times they were invited, and would support banning paintballing or similar activities for under 18s. My solution was to thank the parents for the invitation, but decline with the explicit reason that I do not condone commercial shooting games.
I have also been invited to go paint balling with some guys from the institute, but again thanks but no thanks. Been there, done that, during my military service 30 years ago. Shooting actual weapons at targets that pop up behind windows as you make your way down the main street of a deserted village that had been converted into an infantry shooting range was much more exciting anyway!
CB