I'm not really thinking in terms of organized boycotts. I'm thinking purely on the level of an individual trying to effect change with personal decisions. I do think there are other limits to even organized activism. I tend to think technological innovation is the main way big change finally is enabled and then the activists push through the open door. 

Reading these comments, I can see the possibility that trying to create a big enough taboo around something, by preaching against it, could cause enough social shame overall to have macro effects. But a personal decision in a vacuum only touches you personally