To add some other considerations onto URL shorteners:
- They hurt performance by requiring at least one redirect
- If (when?) they stop working all of their links are broken
- I’m not sure how inevitable this would be if this was done in a decentralized way. Doing it through a sub-domain on ipfs.io doesn’t sound like such a way, though.
- Archive Team has spent a lot of time trying to archive shortened URLs for URL shortening services that have come and gone, leaving a trail of broken links in their path.
- With IPFS, immutability is lost (as @fiatjaf already mentioned). A link that used to redirect to one hash could theoretically be made to redirect to another.
Unless “the core component of sharing in this architecture” involves manually typing URLs, it would be nice to not increase users’ exposure to the weaknesses of URL shorteners.