If you have a co-founder or co-hacker that goes postal, off on their own, acting shady, behaving badly, for whatever reason, you're lost at sea. If you don't have a safety net or savings in place to catch you, you're going to be living on the street. Thanks to someone else.
You can't control other people. Your co-whatever could become a saboteur. The reasons why and how don't matter, it's about the ramification on your life and how deeply it reverberates.
If that's the only thing you have going - your life is wrecked. You're humiliated by being kicked out of what you created. You have to start over, with an added penalty to all your family you can't support, your networking in tatters, and so on. Make no mistake - have a co-founder - you're one person away from having collateral damage done to your life.
And they'll probably make the company tank afterwards. The main reason a co-founder was there was to keep each other's ideas/egos/visions/whatever in-check. Without that personality mechanism in place, the business is rudderless.
So consider me a skeptic to this whole idea of sharing when I coded everything without safeguards in place for myself. That's the exact opposite reason I run my own thing. This is the one thing where I get control.
If you got cash stashed away somehow, or other cash flow sources, you're in a safer spot to take your chances with a co-founder and bounce back should stuff hit the fan.