I work to live, I don't live to work. I flat out refuse to work more than 9-5 and even that is too much. These startups expect you to give them your entire lives, 24 hours a day, and weekends, and eat nothing but ramen.
I don't know about you guys, but I have rent to pay. I need to be paid with real cash, guaranteed. I also need to spend as little time at work as possible in order to earn that cash. I have more important things to do, like sleeping, eating, and spending time with friends and family.
I can almost understand the punk kids who do startups, since they have nothing to lose. I absolutely can not understand the VCs or the rich people who do startups. These people have millions of dollars already. As nice and cool as they may be when you meet them, they are fundamentally in a business of greed. They can already retire to a private tropical island forever, but instead they are going to spend their money making some trivial social web app to squeeze out a few advertising dollars.
That's perhaps the real reason I don't do a startup. Nobody wants to give me money because they know that as soon as the check clears I'll be out the door never to be seen again.