If security finds nearly half the bombs, does that count as success or failure? (Glass half-full or half-empty?) Schneier reckons it's probably good enough, and points out: "Against the professionals, we're just trying to add enough uncertainty into the system that they'll choose other targets instead."
"Do not despair; one of the thieves was saved. Do not presume; one of the thieves was damned."
"One of the thieves was saved. (Pause.) It's a reasonable percentage."