Blockchain-based decentralized messengers

Some of the challenges identified in the article include:

messengers need real-time relay and storage capabilities;
updates on blockchain systems are very rarely backwards compatible;
for a chat application to be useful, you need all (or most of) your contacts to use it, and that takes time, marketing and willingness.

Do you agree with these challenges? Do you have an idea for a solution? If so, the NGI Assure open call might be right for you.

A privacy pipedream?