I decided my current fort's military is tricked out enough to handle a siege for sport and practice, rather than leaving it to the dodge-me trap. My fort has three entrances: One is the dodge-me trap, one is for easy access below the trap for cleanup, and the third is a wide entrance for wagons. I closed off the cleanup entrance, activated an alert, and positioned marksdwarves at the wagon entrance, figuring the dodge-me trap could protect itself.
I watched my marksdwarves pick off a squad of goblins and then a squad of trolls. A few of the enemies had gotten close, so I checked my status screen to see if my dwarf count had gone down. I'd lost a dwarf! So I kept it paused and started looking through combat logs. Marksdwarf fires a bolt, gobbo swings and misses, "it the clothier in the leg" - what?
Zoom! Looked like a dwarf had fallen from the dodge-me trap and is headed up. Unlikely to make it. Well, one dwarf, not too bad. But where was the death? I found that in the combat log, too - on the bridge with the dodge-me trap. Okay, so a couple dwarves got stuck outside when I closed the fast way in, and they tangled with goblins taking the long way in. I unpaused and noticed several dwarves running on the dodge-me bridge - the wrong way.
So I'd lose a few idiots, right? No, not a few. They kept coming. As I watched in horror, dwarf after dwarf ran up, out of the fortress, across the traps, and into the waiting arms of goblin lashers. My military was bored and unharmed at the wide-open doorway below while two dozen were dead and more were injured, locked out, or headed out the door on suicide missions. I double-checked my alert burrow, but it was configured sanely. I looked at the dwarves to see what they were up to, and every single one of them had "No Job" as they ran to their deaths.
I facepalmed, then I raged and yelled at the dwarves, because that always helps, and then I savescummed.