Location, Location, Location

Little Green Footballs has a couple of interesting posts which shed some light on why the UNIFIL observer post in Lebanon was inadvertently bombed by the Israelis:

Canadian General: UN Observer Post Used By Hizballah
Hizballah Firing from Vicinity of UN Positions
Kofi Annan Could Have Ordered Peacekeepers to Leave

In short, if you hang around people who are playing with fire you're likely to get burned.