This writer misses one of the most important issue, which would be under his heading "Validation". Validation isn't (just) internal! It's not that <i>you</i> (necessarily) need convincing your 'idea' is any good.<p>Validation is external. The fact that two people are <i>both</i> working on something makes 'something' 1000x more real than if some guy is working on it.<p>There's always going to be information asymmetry between internal and external: the fact is, if there are two people on the inside, that is one of the strongest signals (to people on the outside, who have limited exposure to the low-level progress) that there is something there.<p>If it's just some guy saying, "Hey I've been building x for the past y" that is a very weak signal.<p>I might even go as far as saying, "The only time you can afford not to have a cofounder is when you can make it all the way to completed product + substantial revenue without having to convince anyone of anything about the future of your business."<p>Anyone includes but is not limited to: employees, partners, your parents, your spouse, and, of course - Investors!<p>If you never need to convince anyone of the future of your project, until it's incorporated, profitable, making payroll - then you might do it alone. But for 99% of us, this does not apply, and a cofounder is one of the best signals around for sharing internal state of validation.