I know I am going to step in it here, but there are some things about this subject that need to be said.
I agree that model and high-power rockets, lacking a guidance system, are useless as a battlefield weapon. They are far too inaccurate to be of any use against specific targets, especially moving targets such as airliners.
That said, I think we will eventually see them used as a terrorist weapon, REGARDLESS of restrictions on propellant. The reason I believe this to be the case is that rockets very similar to "amateur" rockets are already being used for just this purpose in the middle east. See the following link.Please note the difference between "battlefield" weapons and "terrorist" weapons.
On the classic battlefield, a rocket would be used against a specific target in order to destroy that target and/or kill a specific group of enemy soldiers. How accurately the rocket can be aimed is the criterion that determines whether the weapon is "effective" or not.
For terrorists, it is not necessary that the weapon actually hit a specific target, only that it induce "terror" in a general area. A large rocket falling out of the sky from a few thousand feet in a populated area would indeed induce terror, especially if it carried some sort of warhead.
I am sure that there are better and more accurate ways of placing explosives or other warheads on or near a specific target (car bomb, suicide bomber, etc), but that does not rule out the use of rockets any more than it rules out the use of passenger jets.
Given that the technology to produce and use rockets in this manner exists in a fairly mature form in the middle east, I am fairly sure that it will eventually be used here. When this happens, the press is going to be all over us saying, "but you said it couldn't happen!"
I fear the backlash from that event will end hobby rocketry forever.
Ok, go ahead and flame me... Or better yet, prove me wrong. PLEASE.
Bill the Geek