Thank you very much for keeping me out of spoiler-land! I suppose the lesson here is 'don't attempt meta before you've actually watched what you're talking about'.

The point about where a person comes into a series having an effect on characterisation views is an interesting one; I started watching whatever scattered episodes I could find before I bought the DVDs and settled down to watch it chronologically, and I think I probably do think of Sam and Dean and their relationship slightly differently because I didn't start at the beginning. And the fanfiction explanation makes a lot of sense; that hadn't occurred to me.

If you ever have the time to expand on your appeal-of-incest theories, I'd be very interested! I adore Sam and Dean's non-sexual relationship, so the entire point of adding a sexual aspect - for me, at least - is the dirtybadwrong.