I've been thinking about this every since last Monday evening when I was watching CNN and a reporter comes on and says "according to a source at the FBI there would of been casualties if the bombers would of added more stuff to the bombs like nails, screws, pennies, ball bearings, marbles, etc." Thanks for the info. I'm sure the next bombers won't make the same mistake.
If you stop and think about it pennies would definately be the way to go. Have you bought ball bearings, nails, screws, or marbles lately, not cheap. How can you beat a thousand pennies for $10.00.