Something in the real world still has to trigger the divorce condition in the contract. By the time all the legal documents of the divorce are finalized I don't see why a written prenup would be inadequate. Besides nobody is going to store all their assets in etherium. Even if they did how would the contract track future earnings to another account, etc? It's a completely impractical solution to a problem well-served by current means. Like pretty much every other example I've heard. On-chain gambling is the only thing of practical value that I've seen Etherium offer so far.