I really liked/like ZECPages as an example of a fun app using Zcash memo field.
Now, envision a Disqus-like system built on this. Enter a URL, and instantly create a resilient comment thread. As you browse, each site is paired with a discussion (or not – you may need to seed it yourself), immune to downtime. It also archives page snapshots on IPFS (Filecoin), ensuring context remains, even if the site disappears.