The heated debates about same-sex marriage are focused largely on the probable social effects of same-sex marriage, civil unions, and similar legal recognitions of homosexual pairings. My concern here is with a related but distinctly different topic, namely, what will be (and already have been) the social consequences of the political struggle for same-sex marriage. The ultimate effects depend in large measure on the outcome of the struggle, of course, but they also depend on such properties of the battle as its duration and the specific forms it takes. There may be unintended casualties and/or benefifs, and some participants in the struggle admit to goals other than attainment or prevention of same-sex marriage. Together, these possible consequences are what I call side effects. I lack certain knowledge about what these generally undiscussed and unrecognized possible effects may be, but I fear they are largely negative. More optimistically, I think they may be largely avoidable.