Does that mean when a site links to "forum.i2p", then it's up to your own local address book where that actually goes? (Assuming people don't use the ?i2paddresshelper thing for literally every link, unless that is what is done.)
That is correct. And no, people don't use jump links everywhere--only if their site is new and they are passing the links to folks on IRC, etc.
Another thing I forgot to mention: if a name is unknown, your local HTTP proxy will ask you if you want to try to lookup the name from one of several popular "jump services", which are the same services providing address book subscriptions. This is where jump links come from most of the time.
I don't know how i2p works, but isn't that pretty much they way the "normal" net works? If you click a link to "news.ycombinator.com" in your webbrowser, it's mostly up to your local or ISPs DNS resolver where that takes you, no?
True, but your ISP is expected to resolve domains to the same thing as everyone else, which is based on the distribution setup by ICANN/IANA/whoever. I2P has complete control over what a domain will resolve to, and can choose names based on utility to the user. There's also the factor of ease of use: even if everyone could edit their hosts file to make typing domains easier, few people know about the hosts file, or would think to edit it. Putting the option front and center, with a easy-to-use GUI makes a difference.
