Wow. This topic hasn't been touched in a while!
But also, in the book I mentioned before: Confession of a Video Vixen, the author described what she had to go through to 'thank' the rappers for choosing them to be in their videos.
For a quick sexual exchange, millions of people to see your a** on the TV. Sounds like an advertisement. The girl who is willing to 'give' the most, gets the most in return. It's almost like prostitution in a sense. And take notice how you don't really get a chance to look at their face..