Alphaboo and Roxanne both make good points. There's a thread that's really happening right now in Sexy Ams filled with women shot of film, which means that most of the photos were taken before the internet, at a time when, at most, your ex bf was going to show your nude pictures to his friends. So, when you look at those pictures, there's a definite sense of increased intimacy--these are *really* private photos.
I agree with Roxanne's advise for people about posing nude in any circumstance other than someone who likes the idea of millions of others seeing them naked. I must confess, though, that I'm glad that millions of women have made the mistake. A big part of the turn-on for me as a viewer of ex-gf photos, is the humiliation factor. Same reason I like ENF. I recognize this as a kinky way of being, but I think it's part of human nature to intertwine sex with power. That's not to excuse it, but to explain it.