I like the idea of hedging your bets. People always poo-poo working on your startup "on the side," but for some people it makes a lot of sense until you've gotten something built... and it keeps you alive. FeeFighters was largely built on the side, with our CEO working "full-time" as a management consultant to pay the bills (allowed us to hire a designer to gain some leverage, etc)
HN views seem to be slanted on this subject. It's not "hedging" or "being cautious" as much as it is just being smart. Working on a business in your spare time till it makes more money than your full-time job is what most people who have bills and/or families typically do. It's risk-averse, and, if you don't want to quit your full-time job, a great way to make a lot of extra money.
I wouldn't completely call it risk averse. Let's just call it smart and "less risky" than jumping out of a job and into an opportunity that doesn't exist yet.
Maybe I wasn't so clear about this point, but it's also about doing something that may not perfectly fit your passions because of a more reasonable work/life balance and in turn a more doable corp work/start-up balance.
It becomes adjustable risk.
How much more money can a corporate job pay? How much more free time do you have now that you're not putting your own heart into someone else's project? How much do you really need to survive? Now comes the factor that's adjusting your risk.... Salary - Necessity = Liquidity.
How much of your liquidity are you willing to invest in your start-up dreams and how much of that are you willing to invest in your "normal" life? I think that's what really separates the hobby entrepreneurs that never make it and the guys that can in fact make it building something on the side.
Somewhat related: reasons to leave the corporate world for a startup: http://feefighters.com/blog/5-reasons-to-leave-the-corporate...