Why do people post sleazy pictures of themselves on web sites that are accessible to the public?

For quite a few weeks this year I was receiving spam e-mails on my msn account from some users who had made themselves contacts of mine. The e-mails contained links to a dating site that displayed pictures of sexy women who allegedly were from places local or regional to where I live. I initially did not take them very seriously. I was surprised, however, when I thought I recognized somebody in a picture. She had been known to visit dating sites, and she was sufficiently covered in lounge wear.

I was horrified when I thought I recognized a second person on this web site. She is somebody whom I have never met in person and never want to meet. I only recognized her through pictures, or thought I recognized her. The woman was staring brazenly at me through the camera lens, bare-chested. If she is the same person I think she is, she does not need to be on dating sites. Her family has "high" ambitions for her.

When I tried to save the second picture to get a better look in order to verify whether the woman really was the person I suspected her to be, I immediately received a warning of an attempted intrusion into the picture files of the computer. Although I have received occasional warnings from the installed anti virus software about attempted intrusions, I never before have seen such a message about an attempt to intrude into the picture file.

I was wondering if the rational for the actions of people who bare themselves online might be as follows:

"If I expose myself to you you know me intimately; therefore I can rob you."

If the girl in the second picture should become another Hillary Clinton, would this photograph of her naked upper torso be of value to people who want to expose celebrities for their past indiscretions?