I'm interested, for those who think that sexual orientation is 100% non-"choice", here is a thought experiment:
Could, hypothetically, a person be conditioned to be sexually aroused to the sight/context of something they were not previously?
if yes, could that context be a person of the same gender?
and if yes, does that constitute a shift in sexual orientation or can you be aroused by something you arent sexually oriented toward?
also, I've just been to a couple of conferences, where I got to read some upcoming research that talks about very low level visual/perceptual differences between homosexuals and heterosexuals. I don't have it off hand, but could probably get the abstract, however, if these differences do exist, it is almost 100% proof positive that sexual orientation is based more on lower level (genetic, developmental, etc) things than things like "choice"