I disagree with the general disparaging of boycotts etc -- or any form of activism that is non-negative (net result). As Carrol has noted (perhaps in a different context) we cannot know beforehand what actions will lead to positive change because actions do not have linear and continuous development. One big difference that I have noticed between Western leftists and the ones I know from my own past in the East (India) is that the Western variety seem enamoured with determinism (I would call it a form of 'scientism', without resort of parentheses, if I were not worried about a segue). The truth, IMHO, is that, as per the second law of thermodynamics, progress is an extremely unlikely outcome. You cannot "compute" your way to a better world, especially by calculating probabilities.
Actions work in all sorts of ways: creating communities, acting as catalysts for more powerful actions, and so on. Again IMHO, the only way to make progress against the intractable is by continuously attempting the improbable.
The problem, therefore, with modern (20th century and later) leftism is not too much "meaningless" activism, but too little! This is a result, I suppose, of the individualism that seems a defining element of the Western psyche...
--ravi