Lets separate a few things here. There are really only three primary reasons when sex should be considered a bad thing:
1. unwanted pregnancy
2. unprotected sex (unfortunately due to STDs)
3. non consensual sex
The "slut" moniker for women who sleep around is nothing more than another outdated religious leftover bogus sin.
Here's my concern and why I think women get the raw end of the deal between males and females. Some medical nerds can correct me here if I'm wrong, but with men, it's definitely not a good thing to abstain from having sex/ejaculating, be it with another person, your hand, or a mayonnaise filled sock for those in prison.
Full article:
http://www.newscientist.com/article.ns?id=dn4861
Leitzmann and Giles both agree that there are biologically plausible ways that ejaculating frequently might prevent prostate cancer.
"Increased ejaculation may allow the prostate gland to clear itself of carcinogens or of materials that form a substrate for the development of carcinogens," Giles told New Scientist.
Another theory is that frequent drainage of prostate fluid stops tiny crystalloid microcalcifications - which have been associated with prostate cancer - from forming in the prostate duct, says Leitzmann.
Giles notes that neither study examines ejaculation during the teenage years - which may be a crucial factor. But he says: "Although much more research remains to be done, the take home message is that ejaculation is not harmful, and very probably protective of prostatic health - and it feels good!"
I think there's cause for concern anytime you stop a naturally occurring biological function. With all of these new methods of birth control for women, I'm wondering how the studies will eventually turn out on the their long term effects and the resulting lifespans for women who use/used them.