This is the poster child for using http://foundrs.com : virtually incorporate with your co-founders, see how far it goes, when it gets serious convert into a real corporation.
Benefits: no corporate taxes, no accountant to pay. Vesting is automatic (4 years, monthly, just like founder stocks in a Silicon Valley startup). And it's legally binding (thank you copyright law, for once you were useful).
Stock is treated as taxable compensation once/as it vests, whether or not the entity is incorporated. Even worse, because the entity is not incorporated, the IRS could treat the stock as a partnership interest. Partnership tax accounting is a goddamn nightmare.
You could find yourself on the hook for thousands of back taxes plus fines if your "virtual corporation" is successful. And that doesn't even include potential state tax liabilities or self-employment taxes.
Benefits: no corporate taxes, no accountant to pay. Vesting is automatic (4 years, monthly, just like founder stocks in a Silicon Valley startup). And it's legally binding (thank you copyright law, for once you were useful).