CDNs have really assumed the role of ISP-level caching - the good CDNs are co-located with the big ISPs anyway, so the effect is the same. IMO, it's a better so

CDNs have really assumed the role of ISP-level caching - the good CDNs are co-located with the big ISPs anyway, so the effect is the same. IMO, it's a better solution because it allows the content-server much better control over the exact details of the caching and allows stuff like partial caches. The problem with ISP-level caching is just what you suggest: they screw it up.