Back in the days of MySpace, we were working for a client in UK Sports betting (Littlewoods Pools) - and we managed to persuade MySpace to let us have a script tag on the page, pointing to a JS file we controlled.
The script injected jQuery, then we replaced the page with HTML fragments. We had an Adobe Air installer, a Flash game and even had an RSS feed.
Funnily enough today we're mostly working towards using ESI - which reminds me of mod_include back in the day.
ESI is awesome and really connects "let's just cache it" with "but what if this tiny detail in the footer changes and we'll spent hours refreshing the cache". I would've loved to do more with it, but we added a lot more optimization that need to happen before the cache and require access to the whole page, so now I do a poor man's ESI transparently caching all kinds of widgets and shortcodes (Frankenstein's WP).
I guess one could potentially have tiered caches with an optimization layer in the middle and ESI on the backend-facing cache, but that feels extreme and more brittle.
The script injected jQuery, then we replaced the page with HTML fragments. We had an Adobe Air installer, a Flash game and even had an RSS feed.
Funnily enough today we're mostly working towards using ESI - which reminds me of mod_include back in the day.