According to this CNN article, the Air Force is testing JDAMs precision guidance packages on 500 pound bombs. Previously, JDAMs was only fitted to 1000 and 2000 pound bombs. Going with smaller bombs has several advantages. First, a given plane can carry more of the smaller bombs and attack more targets. The article states that a single B-2 will be able to carry 80 of these 500 pound JDAM guided bombs, each capable of hitting a different target. Second, smaller bombs reduce the risk of collateral damage. There's even work underway to develop a smaller 250 pound skinny bomb that will combine high accuracy with a slimmer profile better able to fit into small bomb bays like the proposed UCAV.

This continues a trend that began in the 1970s when a breakthrough in accuracy was achieved with guided weapons. During WWII, hundreds and sometimes thousands of bombers were sent to hit targets in Germany in the hope that enough bombs would actually hit and destroy the target. Today, a single F-15E, B-1, or B-2 can take out almost all of those targets that took hundreds of planes to destroy in WWII.

Early long-range missiles carried megaton (and sometimes multimegaton) warheads because their accuracy (CEP - circular error probable) was on the order of a mile or more. As the missiles became more accurate, most were fitted with smaller (100-250 kiloton) warheads to hit multiple targets. Their CEP had dropped to the point where the smaller warheads had enough power to take out the targets.

Many of the first cruise missiles were fitted with conventional warheads because they were so accurate, they could destroy most targets without having to go nuclear. Even most hardened targets can be taken out if you hit them directly.

Reducing collateral damage is good, too. Innocent people have always suffered in wartime. In those massive raids in WWII, thousands of civilians were killed by bombs that missed the target. In some cases, the accuracy was so poor that the civilians became the target. When the RAF switched to night bombardment, their accuracy was on the order of miles. Since they couldn't hit factories, they went after population centers. "Bomber" Harris, the head of RAF Bomber Command, once said, "It takes 2 years to build a factory and 20 years to grow a factory worker." Fortunately, times and technology has changed.