Not precisely equivalent, but I was involved in a startup where 3 of us split the shares without any vesting agreement in the paperwork. Fast forward 18 months

Not precisely equivalent, but I was involved in a startup where 3 of us split the shares without any vesting agreement in the paperwork. Fast forward 18 months, one of my co-founders was fed up and decided to quit. He claimed (correctly) he was entitled to his 33.3% regardless of future work or any other factors. Of course he would be diluted if there were investments or option grants, but his position was the split represented the full value of our contributions at the start date. After all, he argued, we were paying ourselves salaries for the work we did, so that was our compensation -- the equity was simply an investment that may or may not pay off some day. In the end, we paid him a lot of hard-earned cash to buy back most of his stock over a period of years -- enough for him to live very comfortably without working, while we sweated our asses off to make something of the venture. Probably stupid of us, even though in the end the company went public and the stock was quite valuable for a while. Moral of the story: get the paperwork right or pay the consequences. BTW, quitting co-founder wrote up the founding documents...