1) The lead "coder" was very young and inexperienced, should not that have shaved ~$140M off the max they could raise?
So are many other internet entrepreneurs. Sometimes they make it big, others just disappear, never to be heard from again. Steve Jobs, Bill Gates, Sean Parker, Sean Fanning, Mark Zuckerberg, and many others got started fairly young and made it big. People were willing to bet a lot of money on them. This isn't all that different; just a variation on a theme.
1) The 2) Why did this happen (yet again) and how can similar things be avoided, without interfering with the benefits that can come from a free market environment?
It happened because people do not learn from history, or they believe that they are "special." Visionaries are all snowflakes, believing that they are "more unique" than others, and perhaps they are.
The free market would not be the same if there was nobody willing to risk it all to try something new. So what's the trick to make it work? As a provider of funds (fiat, crypto coin, etc.) your definition of "all" needs to be what you are willing to see disappear with no hope of ever seeing a return.
What's my deal? I "invested" less than I have spent on a ho-hum meal at a purportedly "really good" restaurant with my wife. Am I pissed? Nope. Not at all. I didn't bet more than I was willing to completely write off, if TheDAO fell on it's face, like it did. If TheDAO had hit it big, perhaps with the growth of my investment I could buy a set of dentures when I got older.
Personally I think that Ethereum will survive. Solidity will be fixed, and smart contracts will move forward. In fact I am holding onto my ETH and still running my one-GPU mining rig that earns me about one ETH per week. The "weakness" that was exploited to drain TheDAO was known, as were the ways to prevent it from being exploited, but the writers of the smart contract used to create TheDAO apparently didn't think anyone would exploit it. It was likely a combination of hubris and naiveté. Will it happen again? Yep, that much I know for certain. Just don't ask me when.
For what it's worth, Bitcoin wasn't much different in it's early days. When I stumbled upon it back in late 2011 it was trading hands for about the price in USD as ETH is today. I didn't "invest" in it back then as crypto currency was even newer and less known than it is today. Bitcoin was "Goxxed" and survived, so there is precedent for ETH surviving.
Sometimes you're the bug; sometimes you're the windshield.
Cheers,
- zed