As a customer, I want an easy button to affect my contractors' businesses based on their performance. But when I am on the receiving end, I want to know that the negative reviews are legitimate (not subject to discrimination or gaming) and that the punishment is proportional to the crime. These goals are at odds, and I hope the latter is not sacrificed in the app economy.

You're right that the tourism industry is probably the worst case for democracy to ensure accountability of regulators to the people. But at least all punishments imposed by the government are subject to the court system; the government does not take away your license to make an income without evidence that you actually violated a law. Furthermore, government is subject to other mechanisms to be accountable to the people e.g. FOIA requests (vs Uber, who keeps their data exclusively for themselves). I worry that industries will be controlled by companies that care only about the aggregate revenues and are not accountable to the people,