__ted__

Ending your list with etc. undermines your point. With this header set, can my site track what pages a user views to recommend pages to him later? Can compliant sites keep stats for engineering purposes? Grandparent is dead-on - it's bad enough that this does not affect the behavior of bad actors, but if it isn't even clear what effect it will have on good ones, the false sense of security may be worse than nothing.

The IETF does have a network-layer solution to that.

http://www.ietf.org/rfc/rfc3514.txt