The best, and soon only, good defense against terrorism is a society where people don't want to become terrorists. You guys are thinking in completely wrong ter

The best, and soon only, good defense against terrorism is a society where people don't want to become terrorists. You guys are thinking in completely wrong terms by worrying about countermeasures. You could create 10 grenade-wielding UAVs, set them for a pre-programmed course above the crowd, out of reach of everyone, and set them off almost immediately. Water cannons, oil cannons or any other countermeasure would be useless. This attack is dirt cheap, incredibly destructive and you don't even need a depressed individual to commit suicide to do it. It could be run from any outside location within a couple of kilometers from the target. The only long-term solution against terrorism is to just make sure that people's options in society are good enough that they won't resort to blowing things up. This is also the only sustainable way of fighting crime, which any reasonable study will show you. I'm from Norway, we recently had a terrorist attack that was bigger than 9/11 in relation to our population size. So I'm not saying this as some cold outsider who doesn't see what problems the United States is facing. This is the way things should be handled.