A classic staple of fantasy literature - that a virgin (preferably female) makes for the perfect sacrifice/has some mystical powers tied to her lack of a good dicking.
I mean, it comes from ancient beliefs regarding purity, and fertility rituals, but it would seem to me that a "blank slate" approach might be better - as in, someone who has never been harmed, or soiled by the physical world in any way. But, you run with that, and you're gonna have people sacrificing babies, and it just gets real messy real quick.
It strikes me as something that's hard to fit into a gaming context - after all, most games feature very little sexual content, so staying a virgin isn't too big a deal. And really, it's bad DMing to force them to lose it... no-one wants a graphic rape description during their Happy Fun Adventure Time.
In most fantasy literature, it comes as a property of a supporting cast member - who the Brave Manly Protagonist will end up deflowering at some point. Again, giving this quality to an NPC still doesn't provide much onus to players to make drama out of it - they'll dodge roleplaying sex with one of their friends.
So, I find it's best to leave it to the realm of lesser NPCs (maybe the High Priestess of a temple, or some such), so as to avoid all the complications it might bring. While it might make good background fluff, taking it as a PC is inviting trouble into your doorstep - which, fair enough, is what any good PC background should do, but this one has some nasty resolutions.