An obvious kind of action many folks like to see would be to change the virtual root based on part or all of the full URI, if such information was available. A few people responded with arguments that knowing the full URI had other benefits, many of which I believe to be significant. I'd like to make those arguments again and lobby for the simple inclusion of this optional header. Here are two scenarios that weren't addressed earlier. Both involve the possibility of broken links, something that I think we in the HTTP WG should do our part in preventing.
Professors have their own directories under the respective top-levels.
Many people have URLs that point into professors hierarchies, not just at the top level for the department. The computer science department decides to move their hieararchy to their own machine with a different IP address and its own domain name, cs.bigstate.edu. Unless they want all the links to break, they must put forwarding pointers at every place in the old hierarchy where someone might have make a bookmark. Note that some of the HTTP servers that are supporting different actions based on headers are also supporting server-side includes. The Full-URI header field can be used to indicate the URI requested by the user.