What should be developed on Ethereum?

This was a question posed by Elon Musk to Vitalik Buterin, in what has now become a widely public debate about market creation on a public blockchains. The response of Vitalik spanning across 5 tweets (https://twitter.com/elonmusk/status/1123126001171517440?lang=en) . Each market creation idea is tremendously powerful and can have multiple players that facilitate the decentralization of market functions.

1. Store of value markets : for payments, value exchanges, and for innovative financial products like insurance (hurricaneguard from etherisc). I have widely discussed the economic properties of etherisc in a Managerial Finance journal paper co-authored with their former CTO Alpen Sheth.
2. Markets that manage private identity (e.g., single -signons without giving single firm access to all of an individual's private information that the firm can now use to sell downstream to marketeers) - an approach that has long caught the imagination of individuals and companies but still experiencing difficulties that are related to usability and user acceptance. Imagine remembering 12 or 22 words each time you need to login....or having to download software to login.
3. Markets of registries of public information.
4. New forms of decentralized organizations - this form of organization completes Hart and Holmstrom's - incomplete contracts - hypothesis wherein they argue that firms are incomplete structures of organization for human interactions.
5. Markets for facilitating micropayments across organizations and individuals - this also extends into microfinance and microlending which is a global phenomenon with a hugely unsuccessful business model. Altering financial behaviors of entire societies is a difficult proposition with lots of entrenched incumbents opposing such a move. Nevertheless, such a mechanism can possibly be developed with the right partnerships, incentives, and structures.
6. Markets for data/business analytics - that use homo-morphic encryption to enable private data to be analyzed and modeled without providing access to the actual underlying data.
7. Markets for spam prevention in blockchain-enabled social media- several problems of incentive incompatibilities exist, and greedy user maximization inefficiencies face public social media blockchains e.g., collusion amongst providers as in the case of steemit, bad actors reaping excessive benefits, etc... incentive models that include a combination of recommendation systems, moderation facility, social mobilization, and crowdsourcing can facilitate this extremely complex functionality.
8. Markets for rewards - creating unique reward mechanisms that are based on economics and can just be deployed by either traditional web-based businesses or blockchain-based businesses. These rewards should be based on incentive maximization economics.
9. Stickers and Badges - These are an extension of either art created on the blockchain and of rewards on the blockchain and are valuable propositions.
10. p2p markets for anything that is incentivized - Peer to peer marketplaces for internet connections are already taking shape in the form of helium.io wherein devices that operate with radio frequency transmit the internet over a large area and are owned by individuals and not by firms. the device owners are incentivized by usage in cryptocurrencies.
11. Identity systems, reputation systems, and credit systems for those that are resourceless - these systems could help refugees and several stateless people who have no means of livelihood.
12. Decentralized alternatives to DNS which is today centrally controlled by ICANN and a few government organizations, which can at the word go shut it down entirely.