I disagree. They are designed to instill paralyzing fear in a populace that they are intent on controlling. It's an ancient technique. It will not serve the ends to recruit more terrorists, except when the acts are committed to force recruitment, as was done in VN. The magnitude of the heinousness increases with the resistance of the population to forced control.
In Iraq, the threat that this sort of thing would befall Iraqi govm't troops if they didn't assist the terrorists, is how these guys were captured. It should also be noted, that these contractors are not allowed to mount an effective defense themselves.
The main target of the acts is the civilian populations of the countries opposing them. The ones that have already surrendered are already fearful of them.
Works with Muslims, but Americans are a bit different breed. The more crap like this they pull, the more resolve to fight America gets. And when America finaly decides to realy take off the gloves... Face it, we can wipe Every Single Islamic Nation off of the map in 15 minutes flat, and not even have to leave the US 0f A. The only thing holding us back is mercy, something they simply do not understand. Unscrew the smart bomb tips and screw on the dial-a-booms and set them to about 20 kilotons, rinse, cycle, repeat.
In the evening there is trouble, in the morning it is over, Damacus is a runious heap...