This will be no surprise to most of you.
But the interesting thing, at least to me, is that in males promiscuity is correlated with HIGH self-esteem, and in females it's correlated with low self-esteem.
Quality women with healthy self-esteem actually have fewer bed notches and more long term, meaningful relationships. They don't sleep around or have one night stands. Generally, it's women who are slightly less attractive who fit this criterion. The very attractive women are more likely to have higher self-esteem.
So why does a woman with low self-esteem sleep around?
There are a number of theories, but I think it boils down to this: she seeks constant validation and ego salving through sex with plenty of different males in order to prove to herself that she's sexually attractive, and hence to make her feel better about herself. High esteem women do not need this kind of external validation.
Secondly, by being a slut, she can sleep with higher quality genetic specimens (hypothetically improving her children's reproductive value) than she could otherwise be able to have long-term (i.e. an attractive male will be willing to pump and dump her, but he'll have no interest in a long term relationship because she is not good enough for him).
(However, this second idea is probably unconscious: a psychological adaptation that promotes such behaviour to aid the woman's genes)