Spies do it all the time, right? Maybe this should be called the "infiltration strategy" or something. Sounds sexier.

Although spies do have handlers whose entire career consists of guiding them in their missions, and being a spy is what they are getting paid to do. That seems like a decent amount of social pressure not to defect. I wonder what defection rates for spies are like? What ways are spies selected for low defection probability aside from being citizens of their home country? I've heard that the NSA doesn't like to hire people who have smoked marijuana.