I kinda thought this, but didn't want to be Gloomy Gus, publican edition. Plus it would only be speculation on my part.

The issue is sort of like MTG cards (or any other kind of trading card, really). This layman is reasonably certain that trading said cards is a taxable event, even if one that is generally ignored. The difference here is that everyone, including the IRS, has an indestructible virtual paper trail of every crypto-collectible interaction.

This is, among other reasons, why I never involved myself with CryptoKitties. Hopefully some reasonable Congress will pass some reasonable de minimis crypto exception to allow this sort of thing to flourish without having to worry about the taxes of it all.