My wife is kind of like the original poster. She is not comfortable with me looking at porn, basically due to her insecurities, which she admits, and due to an ex-boyfriend who apparently made her feel insignificant due to his obsession with porn. It's tough for me because I, like many men out there, like to view porn on occassion. I have to hide my personal collection and view it when I'm alone. I do wish I could share this side of me, but I know my wife would be uncomfortable. I actually wouldn't be surprised if she suspected that I do look at porn because she knows how much of a pervert I am.
We did actually watch porn together a couple of times, and had a good time with it, but after the fact, my wife became paranoid that I would be less turned on by her because of it. She knows how sexy I think she is, and knows I will never cheat, but my viewing porn is something she just can't accept.