A possible exception seems to be virgins. There's a lot of debate over whether it is acceptable to be dishonest about a lack of sexual history. Anything short of revealing that you are in fact a virgin prior to having sex is akin to having sex under false pretenses and possibly sexual assault.
I think we need to step back for a moment and think about this. For one, I think the only people who would be upset about having slept with a virgin are people who are looking for casual flings or hook ups rather than meaningful long term relationships. I have no experience with having sex with strangers, but I'd imagine people at bars or clubs are not exactly completely honest about themselves prior to having sex. You might wear makeup or high heels to make yourself look better or maybe you're taking law school classes at night and you fib and say you're a lawyer. Stuff like that. I don't think you talk about your hangnail or how you found a bunch of hair on your pillow this morning and you think you're going bald. I could be wrong though.
Now some of you might say "well, lying about your receding hairline, or occupation, or sprucing yourself up isn't the same as lying about having had sex before". And you're right, it isn't the same. But how's the person lying supposed to know what kind of thing you might find to be a turnoff? Moreover, is there really a responsibility to protect you from being turned off?
Disclosure rules are really designed to protect you from any negative externality that might harm you in some way. Your stock broker discloses to you how he's investing your money because his decisions will effect your net worth for example. If we're talking about sex, disclosing to you that I have an STD is important because you could catch it from me. You can't catch virginity nor can you catch bad sex. So I can't say that I entirely agree that it's incumbent on the inexperienced sexual partner to be upfront about his or her inexperience. If you don't like the sex they have with you you are free to never see them again and there will be no further impact on your life.
A big point often brought up is that sometimes virgins become obsessive about the first person they have sex with. And I agree that it's possible, perhaps even likely to happen. But I'm going to let you in on a little secret about some of us inexperienced people: we get a little obsessive whether you sleep with us or not. I have never stalked anyone and don't plan on starting, but I will admit that I do google people I went on dates with or had a crush on years ago. If you shared a drink with a guy and he tells you he's a virgin so you decide not to sleep with him, it's not like he's not going to get obsessive. You might not see him ever again but he's probably googled you, or looked you up on facebook. You're not really saving yourself anything except a terrible roll in the sack.
In an ideal world everyone would be honest and virgins would accept rejection and go find people willing to date or sleep with virgins. The problem is virgins tend to be virgins because they have a hard time finding someone they like who also likes them. I think about my own situation; my last date was at the beginning of last May. Here we are on April 20, almost a year later. If you want to know why people are willing to hide their faults in order to find a romantic or sexual partner, that's why.
None of this (by the way) obligates you -experienced person- to have sex with a virgin. Nor does it obligate you to have sex with someone who doesn't wish to disclose their sexual history. My advice to you is that if it is that important to you, you have every right to ask and you have every right to walk away if the person isn't open to disclosing anything with you or if you suspect them of being dishonest. But you don't have a right to demand that they disclose their sexual history to you. That's theirs to decide what they want to do with it.
I'd love to live in a world in which we can all be more honest about sex. A lot of people want to blame society, sexism and sex-negativity for why we can't. I think it's more likely our own fears and insecurities that causes the problem. Let's hope it changes.