The biggest danger from startups as I see it isn't even the financial loss. That's very bad, don't get me wrong-- $100,000 losses aren't uncommon-- but it isn't the worst thing. The worst thing that comes out of startup failure is the confluence of opportunity cost with the extremely harsh age-grading of VC-istan.
Most industries give you 25 years to build a career, and then 15 more on the plateau before you even start to worry about age discrimination. That's something people start to face in their 60s, not 30s. In VC-istan, you have much less time and losing 2 years to a dogshit startup is catastrophic. The loss of opportunities even between 25 and 30 is a substantial drop. By 35, if you're not retired or an executive (never mind whether you actually want to manage) people start to ask what happened.
VC-istan is a hypocritical culture, because it superficially champions risk and failure, but if you don't have an unbroken stream of successes, you become yesterday's dogshit pretty much immediately. What "we accept failure" means in VC-istan is that people with the political skill to make their failures appear to be someone else's fault can continue their careers uninterrupted, but how is that different from the rest of Corporate America? It's not. VC-istan is just as narcissistic and intolerant of missteps. If you're not VP/Eng by 35 and a Founder by 40, goodbye.
The real calamity you risk in a bad startup is the career damage. You can easily end up in a position well below your level of ability in the next job, and once that happens, you're screwed because most people get bored rapidly and lose motivation when this occurs. I have no idea what happens to the people who fall under their age curve. I hope to never find out.
It's no wonder why people are so depressed. A world in which the aging process starts so prematurely is depressing. It's like modeling, but with uglier people.