In Hyper-G[1] and prospero[2], the links are maintained much less by
hand, and much more by the machine. Prospero employs a notion of "time
to live" for links, so that stale links just go away after some time
(I think).
I expect that over time, link addresses will be maintained
independently from document content; I'm not sure if HTML will change
to accomodate this, or if document content and addresses will be
"merged" into the current HTML format on the server side.
I am seeing more and more motivation to maintain links separate from
content all the time...
I don't have time to look into the details right now, but folks cooking
up solutions would do well to investigate those systems.
[1] Hyper-G W3 Entry Point (Informationssystem der TU Graz / DVR: 008 1833)
http://www.tu-graz.ac.at:80/CHCIbib/
[2] ftp://prospero.isi.edu/pub/prospero/doc/