Decentralised marketplace, maybe? Open-source, trustless. So people can't scam you. Not saying that blockchain is a good way to do this: For instance, privacy would be a major red-flag, as well as the question of who's going to do the mining.

[edit]

Just found this: https://openbazaar.org/ Doesn't appear to use its own blockchain. Does use cryptocurrency though, for largely privacy and anti-censorship reasons. Uses multisig capabilities in Bitcoin to enable escrow/chargeback.

As to why you wouldn't do the same thing for bananas: Weed is illegal, so any business selling weed is in danger of being shut down. Something decentralised is more immune to getting shutdown. Compare Napster (centralised) to BitTorrent (decentralised).

As I said:

> I conjecture that blockchain only solves peer-to-[peer] digital currency

You kinda just described something like Silk Road right?