The power of non-nuclear bombs

The US has been bombing the bejeezus out of Bagdag yet there seems to be more targets worthy of being hit - or targets worth hitting again. I’d think, with the power of bunker busters, MOABs, etc. that we’d be doing nothing more at this time but make the rubble bounce.

From a layman’s point of view, just how much power is packed into these bombs and how much can be delivered to the target effectively?

The newspapers give the MOAB at 21,000 lbs - what’s that really mean? What would happen if I dropped it in the center of the Pentagon’s central court? A lot of new windows? Removal of the inner ring? Building just a memory? What would happen if I hit my local shopping mall with a bunker buster?