For example, there exists a smart contract for marriage, known as I want half. Does the corresponding property have to exist in Ethereum too? Where will the contract gain knowledge about the IRL assets of both parties? And how can it trust the source of that knowledge?
If there is a contract about lending money with interest, what if the borrower gets "bankrupt"? How does that work?
Do all dApps have to be "open-source"? What if someone develops a similar app with the same smart contracts as competition, by cleverly imitating my code?