What would be the repercussions of everyone switching to per-site/customer caching, recursive resolvers instead of per ISP resolvers?
On the one hand if we assume the customer to ISP ratio to be about a million to one then the volume of traffic on popular nameservers is going to go up a huge amount.
On the other hand thoughif your nameserver is now required to handle millions more queries per second then either you are a central piece of infrastructure like .com or a high traffic service like cat.videos.example.com. With the latter, you’ve been handling millions of HTTP queries per second anyway. You’ll just have to handle massive traffic volumes for DNS now, too.
The end user is accustomed to the DNS part taking 10ms and tbd HTTP part taking 1000ms. They would probably now have to suffer the DNS part taking 100ms to 1000ms as well.