I refused to watch the 2008 Summer Olympics because of China's human rights abuse. I'm not much into the Olympics anyway, but some of my favorite softball players were on the US team and that was the only thing I really hated to miss.
There are certain authors I refuse to read because of their behaviour towards people who don't kiss up to them or they're plagerists. Lee Goldberg, Victoria Laurie, Laurell K. Hamilton (plus she's a crap writer), Cassie Edwards, Cassie Claire, and Janet Dailey are ones I absolutely refuse to read.
But for the most part, I find boycotts stupid and confusing.