While Iraqi irregulars were disappointed at the effectiveness of their RPGs against American armored vehicles and troops, the weapon is still very useful against just about every other military force in the world. And many irregulars spend a lot of time making war on civilians, where the RPG is a terrifying weapon. Firing an RPG at the wooden hut that a hostile (to your cause) family lives in, sends a message, even if it doesn't kill anyone in the building.
Why All Those RPGs? Like irregular armies the world over, Iraqi fighters who attacked American troops loved to use their Russian made RPGs (Rocket Propelled Grenades). The RPG was developed from World War II "bazooka" type weapons and introduced by the Russians in 1961. The current RPG 7 weighs about 17 pounds, with most grenades weighing five pounds each. American tanks and M-2 Bradley infantry vehicle (with additional appliqu armor) are mostly invulnerable to RPG fire. During the Iraq fighting, it was common for most of the armored vehicles in a unit to be hit at least once by an RPG round. The real damage from RPG fire was the fragments from the exploding grenades. Even the anti-tank round (the most common fired by the RPG) would throw out wounding fragments for 10-15 feet. These rarely killed, but troops were often wounded in the arms, legs and face, and often put out of action for a while. But most armies, and irregulars, like the RPG because it is cheap, easy to use and very effective against troops lacking protective vests and helmets. The RPG is also effective against many other armor vehicles. Most RPG anti-tank rounds can penetrate 12-20 inches of ordinary armor. But most modern tanks no longer have ordinary armor, which is why the U.S. M-1 tank and M-2 infantry vehicle can take an RPG hit and keep going. The RPG launcher costs anything from $100-$500 (lotta second hand stuff out there.) The most common RPG ammo is the anti-tank rocket and these go for $50-100 each. This adds up, as you have to fire a dozen or so rounds to develop some accuracy. Unlike the launchers, RPG ammo doesn't get cheap, unless some wealthy nation is flooding an area with it, because the ammo gets used up and the launcher does not. Without much practice, a user can hit a vehicle sized target most of the time at ranges of 50-100 meters. As an operator fires more rounds, he becomes capable of hitting stationary targets at up to 500 meters, and moving targets at 300 meters. It's this last skill that has made the RPG dangerous against helicopters. Irregulars also like using the RPG as a form of artillery. Get a bunch of RPGs firing at the same area say, a kilometer away, and you will do some damage to any people walking around. The rather more rare anti-personnel rockets will spew out fragments up to 30 feet or more.