I've gone through this thread several times, and I really agree with most of the reasons that you stated, they certainly have merit.
I think that by now I should explain why I opened this thread in the first place:
Being with someone is never a black or white situation, as with all the things in life is, most of the time we dwell in the grey area, and I have a feeling that as time passes by we push our boundaries, and those things that once were our deal-breakers are not that any more, because everything else seems to outweigh that one thing that was a deal-breaker previously. I'm not really sure where the line should be drawn, or at what moment in time we exactly become aware that enough is enough.
I'm not sure if this was clear enough explanation, I'm not sure if you ever have been in this situation.
I was one of those people who used to say that I wouldn't tolerate infidelity, but over time I came to the conclusion that in this mater things are never black or white, and that under some circumstances I could see myself forgiving it. My boundaries have changed. Now I have a hard time defining them for myself, a big part of me opposes to all those black and white views, though I am aware that having clear boundaries, even if to have something to move from time to time, is necessary.