[cleverjake]

The last time I had to deal with this it was a result of links to a site from an email being attached to the user it was sent to (eg example.com/?email=[e-mail]). It was not a wonderful example, just a quick one. The moral being by caching query strings you risk needing to parse the ones being passed to ensure there in not unnecessary caching.

[ZenPsycho]

This use case seems abusive to me. I don't mind breaking abusive use cases.

[cleverjake]

Neither did XHTML.

Web Standards work requires you put up with a ton of really stupid things that people have been doing for a long time.

[ZenPsycho]

I don't mean abusive in the sense that it's using technology in a way it was not intended to be used. I mean abusive as in actively harmful to the user's interests and privacy.