The impact of the foot-in-the-door phenomenon is most clearly illustrated by

The destructive obedience of participants in the Milligram experiments.

Explanation:

The foot in the door technique is a persuasive technique. It persuades people so that people will agree at a particular task. It is based on the idea that if the respondent will accept the small request than they can make them apply a big request, which will be more significant.

For that request, they know maybe not accepted. This strategy is used by the salesperson from door to door. This is a useful technique in the type of sales too.