Oh man! I didn't mean to confuse anyone! This is what happens when you only let four hours lapse between first getting the idea to posting. My bad.

Pam, Lisa and alcyone have the right idea. (And I'm LOL that the words "moral fiber" can be applied to a story of mine without a trace of irony.)

Lois started out frankly curious about the suit and its ability to be removed. And then she realized that she really was seducing Superman. So, like alcyone said, she backed off because she wasn't trying to seduce him solely for the sake of being able to do so. He had shown her that he was willing to trust her and show her a part of himself that no one ever sees. So she destroyed the pictures to prove to herself that the experience meant something to her - something that wasn't worth exploiting.

At the end Clark realizes the same thing.

Lois: You know, I have a funny feeling that you didn't tell me your biggest secret.

Clark: Well, just to put your little mind at ease, Lois, you're right.
Ides of Metropolis