I don't get it. Even if Mathews performance would have been underwritten in ths way, would there have been a reason to trust him in hindsight? If not, then this system would have failed, and propably not only in this obvious case.
Matts bet (as stupid as it was) does highlight that trust has limits. Prior to the bet I would have trusted Matt with a couple BTC, maybe even a couple hundred BTC, but 10,000 BTC requires a lot of trust more than just someone's word. 80,000 BTC even with a signed promissory note is just silly, ask your bank if they will give you a $1,000,000 unsecured signature loan.
The issue is betteors looked at only THEIR tx not Matt's tx. Bettors should have asked themselves this questions:
"Would I be willing to transfer 10,000 BTC to an address Matt controls and trust him to transfer it back?"
If the answer is no they shouldn't have placed the bet. It indicates they didn't trust Matt to pay 10,000 BTC based only on his word. Matt's bettors while individually placing small bets, were collectively (maybe unknowingly) trusting Matt to pay almost a million dollars. Someone betting 50 BTC wasn't trusting Matt to pay 50 BTC. Why would Matt pay 50 BTC and default on the other 79,950 BTC? Obviously he wouldn't. Either everyone was going to get paid or nobody would. I don't trust anyone that much and certainly not anyone online.
"Trust-bonds" could be setp with limits (i.e. I pledge 5 BTC that ripper234 won't bust a trade of up to 100 BTC). The cap could be set based on how much the person trusted the other person. Trust bonds should also be revocable with a delay. I trust ripper234 (to use him as an example) but if opened a "magic investing biz offering 7% per week" I should be able to revoke that trust. His actions make me trust him less (enough so that I would no longer want to back it with funds). The fact that he hasn't scammed anyone yet (in this scenario) doesn't matter. It is possible that someone's actions can reduce trust long before they commit fraud.
For large transaction escrow is the only way to go. Vlad made a 5,000 BTC bet but it was escrowed. Neither party had to trust the other (although they did need to trust the escrow agent). Where "trust-bonds" could be useful is smaller tx where the incentive to scam is less and the complexity and cost of an escrow is not worthwhile. The only bad thing is I can't see how this can be done completely decentralized. Semi-decentralized maybe ...