There are ways to do in-app purchases for kid apps that aren't unethical. In fact, allowing people to try your app before buying it is a very ethical thing to do. Don't limit yourself unnecessarily, and don't assume kid apps with iAP must be from shady developers.
I know you feel like everyone is being unreasonable about this, but instead of trying to change their minds, consider it market research: parents on hacker news overwhelmingly distrust iAP, and maybe that means some other form of try-before-you-buy would be more appropriate for kids' apps.
I believe windows phone market place and android allow you to do some sort of trial but I don't think you can do that in apple app store. I'm not 100% sure about this so please correct me if I am wrong.
You are correct. There are a lot of kid apps with iAP that offer great value such as additional levels etc. I purchased some my self. It's the smurfberry kind of iAP that I don't like.
I absolutely agree with that. What disappoints me is how quickly HN parents will shut off their brains and have a knee jerk reaction to an otherwise really handy feature. And in most cases, if they really hate iAP that much, they could figure out that an app isn't for them before downloading, and save themselves and the developer from a negative situation.
Which makes me wonder what kind of parents are downloading apps and handing over the iPad without doing any research (since certainly if they were doing any research at all, they'd know it used iAP beforehand).
