I have ignored multiple posts, assuming they were trolls, dissenting the slut double standard. i.e. Why are men encouraged to sleep around, while women are readily discouraged? In good faith, I will try to answer this question with some of the resources I have stumbled across. Please add to the discussion below.

Promiscuous women are more likely to divorce

Taken from the social pathologist's blog:

Cohabitation, that is "living together" before marriage has been shown to increase the risk of subsequent divorce of a couple. Many investigators have felt that the practice of cohabitation is selective for people who don't value marriage highly and hence are more likely to divorce when stress is put onto the marriage. In essence, it was thought that the cohabitors more "liberal values" placed them at higher risk of divorce.

Jay Teachman, an academic, investigated this matter further. The study, which is available online, makes for interesting reading. Teachman's genius was to look stratify the cohabitors risk of divorce by the by the number of sexual partners/cohabiting history.

The study was based on data from the National Survey of Family Growth 1995 cycle and involved over 6500 women.

It was controlled for a host of variables.

The study was in no way sponsored or funded by any conservative organisation.

Teachman's conclusion: The results presented in this article replicate findings from previous research: Women who cohabit prior to marriage or who have premarital sex have an increased likelihood of marital disruption. Considering the joint effects of premarital cohabitation and premarital sex, as well as histories of premarital relationships, extends previous research. The most salient finding from this analysis is that women whose intimate premarital relationships are limited to their husbands—either premarital sex alone or premarital cohabitation—do not experience an increased risk of divorce. It is only women who have more than one intimate premarital relationship who have an elevated risk of marital disruption. This effect is strongest for women who have multiple premarital coresidental unions. These findings are consistent with the notion that premarital sex and cohabitation have become part of the normal courtship pattern in the United States. They do not indicate selectivity on characteristics linked to the risk of divorce and do not provide couples with experiences that lessen the stability of marriage. Executive summary: It's not the liberal values, it the number of partners that matter.

And,

This limitation notwithstanding, the results presented here should shift attention away from research that focuses on the selection of individuals into cohabitation and premarital sex to a focus on the selection of individuals who do not marry the individuals with whom they first cohabit or initiate first sex. It may well be the case that, irrespective of the legal status of the relationship, the relevant distinction to make is between people who form multiple relationships and people who form a single, longer lasting relationship.

TL; DR: He also super imposes Teachman's findings onto the heritage study.

Promiscuous women have an elevated risk of depression

There was a study done on college students a while ago, No Strings Attached: The Nature of Casual Sex in College Students, The Journal of Sex Research, Vol. 43, No. 3, August 2006, pp. 255-267.

On page 263, there's a chart that clearly shows this relation

Further up, on page 259, so you can understand what the charts saying:

The CES-D was developed as a self-report instrument to measure depressive symptoms in the general population. Higher values signify more symptoms of depression. A score of 0-14 has been found to be equivalent to the levels of depressive symptoms in the general population; a score of 15-36 has been found to indicate the individual is "at risk" for depression; and a score of 37 or higher has been found equivalent to scores found in clinically depressed individuals.

TL; DR: Men's depressive symptoms were roughly unaffected by their number of sexual partners; in contrast, as women have more sexual partners, they have more depressive symptoms.

Bonus: A gem from PhysiciansForLife.org

According to a study reported in Pediatrics, early sexual activity leads to serious behavioral problems. Of 1500 girls studied, non-virgin girls were 2.5 times more likely to have used alcohol than virgins, 6.2 times more likely to have smoked marijuana, and 4.3 times more likely to have attempted suicide...

Why it is beneficial for men to engage in promiscuous behavior:

Women prefer taken men

Evidence of mate choice copying in humans? The chateau delivers.

Offered a single man, 59 per cent were interested in pursuing a relationship. But when he was attached, 90 per cent said they were up for the chase.

Men were keenest on pursuing new mates, but weren’t bothered whether their target was already attached or not.