I realize I'm late to the topic of sexual experience (or lack thereof), but I just had to stick my head in and mention that I was put off by the pooh-poohing of the idea of older virgins a few pages back. Believe it or not, it actually is perfectly possible to make it to one's twenties or thirties or beyond without having slept with someone. Personally, I'm a 29-year-old virgin, and I know several people in their mid to late-thirties who are also virgins. Not saying we're common, but we're also not unicorns.
Also, can we not with the implication that one has to have had sex to be "worldly and mature"? With regard to Cassandra specifically, are you telling me that you would look at a woman who has traveled throughout much of the known world, ferreted out assassination plots, saved the Divine from being eaten by a dragon, risen to near the top ranks of a secretive and feared organization, and earned titles like "Hero of Orlais" and "Right Hand of the Divine," and still, upon finding out she's a virgin, cry "NOPE! Not worldly and experienced enough for me!" Because...yeah. I'm pretty sure there's more to life and the sum total of human experience than whether or not one has had sex. Ditto for the tired old claim that people who don't regularly partake in "physical intimacy" are somehow broken, dysfunctional, or otherwise abnormal or less than human. That may or may not have been how those comments were intended, but trust me, when you hear it as often as I've heard it, that's how it starts to come across. And it's really dismissive and offensive to people who are asexual, or who, like me, simply choose to be celibate.
To bring this slightly more on topic, while I don't expect Cassandra to be a virgin (and don't have a strong opinion on her prior sexual experience either way, because...that's a little creepy), I think it would be cool if she was. In media, older virgins ("older" being anything past, say, 20) are either nonexistent or the butt of jokes. I wouldn't expect BioWare to take the latter route--or at least, I would hope not--and I definitely can't see Cassandra as either the "blushing, skittish virgin maiden" archetype or the "socially hopeless desperate nerd" archetype. I would find it really refreshing to interact with a character for whom virginity is simply a state of being, not a disease they need to be cured of.