@aral remote media caches expire very frequently and yeah it's kind of embarrassing, but,
a better scenario is one where your home server can fetch missing media from the source server for the client. keeps traffic routed through the home server where it belongs, preserving privacy and caching it for everyone on your instance.
it's the web but also it's really not? AP and existing AP implementations have as much in common with email and Usenet as they do with conventional web scenarios. and if we're giving up the home server's role in caching and access control, we should be trading it for something *better* than the web at scaling, like torrents.