It does seem too obvious. But maybe *some* of these guys ARE stupid. Saddam and his "baby milk factory" ploy seem to have been a genuine attempt at propaganda.
How would having decoys get arrested benefit the terrorist network, unless it were to siphon off counter-terrorist manpower?
It siphons off the manpower of investigators, chasing after purposely dropped "leads." The small fry sacrifice themselves while the big fish get away quietly. They've got plenty more people to waste and who are willing to get wasted.