I personally don't see how they can tax it since it is not federally regulated. That is just my personal opinion. No verification of transactions.
My idea is to make investment anonymous. Investors would supply a receiving address along with their payment. Investors would only be referenced by their receiving address. To encourage trust in the operator,
the operator would regularly post a semi-public record of payments and mining profits which would be available to the investors. Investors should be able to verify the records, otherwise it looks like a shady scam.