Hackers themselves can't tell how good they are. This is true to a degree in most fields. I've found that people who are great at something are not so much convinced of their own greatness as mystified at why everyone else seems so incompetent.
In a low-tech society you don't see much variation in productivity. If you have a tribe of nomads collecting sticks for a fire, how much more productive is the best stick gatherer going to be than the worst? A factor of two? Whereas when you hand people a complex tool like a computer, the variation in what they can do with it is enormous.
Perhaps great hackers can load a large amount of context into their head, so that when they look at a line of code, they see not just that line but the whole program around it. John McPhee wrote that Bill Bradley's success as a basketball player was due partly to his extraordinary peripheral vision. "Perfect'' eyesight means about 47 degrees of vertical peripheral vision. Bill Bradley had 70; he could see the basket when he was looking at the floor. Maybe great hackers have some similar inborn ability.
The key to being a good hacker may be to work on what you like. When I think about the great hackers I know, one thing they have in common is the extreme difficulty of making them work on anything they don't want to. I don't know if this is cause or effect; it may be both.
Your business success will depend on the extent to which programmers essentially live at your office. For this to be a common choice, your office had better be nicer than the average programmer's home. There are two ways to achieve this result. One is to hire programmers who live in extremely shabby apartments. The other is to create a nice office.
It seems surprising to me that any employer would be reluctant to let hackers work on open-source projects. At Viaweb, we would have been reluctant to hire anyone who didn't. When we interviewed programmers, the main thing we cared about was what kind of software they wrote in their spare time. You can't do anything really well unless you love it, and if you love to hack you'll inevitably be working on projects of your own.
Even if your startup does tank, you won't harm your prospects with employers. To make sure I asked some friends who work for big companies. I asked managers at Yahoo, Google, Amazon, Cisco and Microsoft how they'd feel about two candidates, both 24, with equal ability, one who'd tried to start a startup that tanked, and another who'd spent the two years since college working as a developer at a big company. Every one responded that they'd prefer the guy who'd tried to start his own company
Startups almost never get it right the first time. Much more commonly you launch something, and no one cares. Don’t assume when this happens that you’ve failed. That’s normal for startups. But don’t sit around doing nothing. Iterate.
Great software, likewise, requires a fanatical devotion to beauty. If you look inside good software, you find that parts no one is ever supposed to see are beautiful too. I'm not claiming I write great software, but I know that when it comes to code I behave in a way that would make me eligible for prescription drugs if I approached everyday life the same way. It drives me crazy to see code that's badly indented, or that uses ugly variable names.