They charge a variable rate based on the nature of the business and the risk it involves. Porn sites get charged 10-20% in credit card fees because of the high number of chargebacks.
IceCreme? We can't refuse you, but it's $4500 for you!
Where do you draw the line? Litigation is expensive!
I'm speculating that fraud would be lower than average for such transactions, because there's such a strong paper trail from the instacheck system and all.
Sounds like offering VOIP related stuff would also be a no no with them, so I guess if you made a chat app with features similar to Skype, couldn't use stripe either.
It sounds like some of these rules might be passed down by one of the major credit card processors, but I know there's other providers out there who allow this stuff but maybe higher fees or more vetting for a merchant account.
https://stripe.com/restricted-businesses
As for the virtual world idea, I have debated about using blockchain since I know some other virtual worlds experimented with doing blockchain based payments, so could probably mix decentralized and centralized but I think not having a stable value kinda sucks, then non technical users setting up a wallet and other considerations, especially if multiple devices is kinda a UX nightmare. Well I guess you could make a wallet on your phone or desktop app, and try to enter the seed words in your VR headset too but probably be strange to most people. Micro transactions where speed matters is also a hurtle...