> f I have to trust you to give me back my $10, I'm never contributing to your code. Ever.

That's the whole point! Either you are willing to trust the money to someone you don't know, or you will have to find another way to establish social proof.

> you glossed over my banana joke,

Sorry, not the biggest AD fan. Anyway, I am saying people will have to "pay up or establish social proof". Charging from a family member is not the same.