Better Living Through Technology Dept.

One of the more popular ideas for a modus vivendi for Israel is for them to just build a bloody great defensive wall, and let the Arabs on the other side stew in their own juices. The great objection to this is that when a similar idea has been tried, e.g. near Lebanon, all that happened was that the Israelis within about 10 km of the border suffered periodic random artillery bombardment, from everything from portable rockets to large artillery pieces. The only way to stop this was to actually hold the ground they'd be firing from as they do the West Bank. Immediate air-attack on the launchers/guns stops repeats, but still doesn't protect civilians against the first shells. It's also useless against small rockets fired randomly using a timer. And as Israel is so very small, a 10 km buffer zone inside the border would be untenable.
So why are the Israelis building exactly such a wall now? From CBS comes a possible answer :

A joint U.S.-Israeli laser designed to protect northern Israel from missile attacks downed its largest rocket to date during a test over the southern New Mexico desert.

The ground-based Tactical High Energy Laser, or THEL, locked onto and destroyed the 11-foot-long, 6-inch-diameter rocket in flight over White Sands Missile Range on Tuesday, Pam Rogers, a U.S. Army spokeswoman in Huntsville, Alabama, said Friday.

The stationary test version of THEL has shot down smaller Katyusha rockets and artillery shells in the past, she said.

The system, which eventually would be mobile, uses an advanced radar to spot and track incoming rockets and then fires a deuterium fluoride chemical laser to destroy them.

Israel's director of weapons systems and infrastructure development, Shmuel Keren, said the system is able to intercept a variety of aerial targets such as long-range rockets and cruise missiles, to which there is currently no solution.

THEL, being developed by Northrop-Grumman Corp., has passed tests at White Sands since 2000, said Bob Bishop, the company's media relations manager in Redondo Beach, California.

The company could deliver a mobile prototype by 2007 or 2008 if it gets a contract this summer, he said, adding that the project appears in the U.S. defense budget for fiscal 2004 with a $56 million allocation.