The main issue with net/http is that it generates a lot of garbage which is definitely going to show up in your profile if you're handling a lot of requests per second.
The purpose of Mining is not to hand out new coins, this is only done to incentivise mining. The real reason behind mining is to secure the transactions. Mining prevents people from double spending their coins.
Yes both Chrome and Firefox would automatically try the next IP when I checked a couple of months ago. We used to use this for load balancing, returning the IPs of our servers in random order. Even when one of the servers would go down we wouldn't loose any traffic as browser would just use the next one.
Yes I have noticed the exact same thing on Reddit lately. My guess it's because they started sending "Cache-Control: no-cache" which prevents Firefox to cache the page for the back button.