You are right, except in cases where defecting on the boycott is more harmful to you than not defecting. For instance, if I am a scab and cross a picket line,

You are right, except in cases where defecting on the boycott is more harmful to you than not defecting. For instance, if I am a scab and cross a picket line, I can put myself in danger or at least make myself unhireable in the future. In this case, though, people can be hired without anyone knowing about it. If lots of money is offered, someone will take it, and if there is pressure not to do take such a job, they will simply keep it secret who takes the job. I think what you are saying, which I absolutely agree with, is that any system that relies on people going against their own personal self-interest, in mass, is doomed to failure.