[davedx]

This is what HTTP redirects are for:

http://support.google.com/webmasters/bin/answer.py?hl=en&...

[chalst]

That isn't very useful if you are not sysop of the site the old content links to.

[davedx]

Of course. The responsibility for maintaining a link lies with the linked to site. My point is there are mechanisms that allow the links on the web to change without breaking it.