I really like your idea, but what about content being changed/updated, instead of deleted?
For some use cases it would make sense to show the cache (when the original quote is no longer there), while for other it'd make sense to forward (some style update, or an important addition).
- Allow someone to manually view the cached version at any time if they wanted to.
- Show a splash page giving the user to view the original or the new version (complete with a diff highlighting changes?)
- Code some heuristics, similar to Instapaper and the like: if the content of the page changes, display the cached version, but if it's just the layout that changes then display the new version. Or look for dates on blog posts, or words like "Updated: " or similar.
- Give the website owners control: let them submit their site to be linked against, and give them some metadata tag that they can use to flag updates. This sidesteps the rights issues too (the website owner gives permission) and it could also be used as a CDN essentially, or a backup in case of server failure, or if the website is hosted in an unfriendly country etc.
I think it's definitely doable in theory at least.
It occurs to me--this is exactly what http://semver.org/ is for! Content changes are new "major versions"; edits are "minor versions"; errata are "bugfixes." You could link to a page @14.1.2, or @14.x, or @latest.
For some use cases it would make sense to show the cache (when the original quote is no longer there), while for other it'd make sense to forward (some style update, or an important addition).
How do you think can such service handle this?